`Import type` should be used in place of `import` to prevent future errors

[esquevin]

Running Deno 1.4.0 with the --unstable flag raises a lot of errors:

error: TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { ErrorStatus } from "./types.d.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/httpError.ts:30:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { ErrorStatus, RedirectStatus } from "./types.d.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/util.ts:12:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { BufReader } from "./buf_reader.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/headers.ts:3:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { ServerRequest } from "./types.d.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/body.ts:7:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { HTTPMethods, ServerRequest } from "./types.d.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/request.ts:14:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { Request } from "./request.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/response.ts:4:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { ServerResponse } from "./types.d.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/response.ts:5:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { KeyStack } from "./keyStack.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/cookies.ts:6:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { Request } from "./request.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/cookies.ts:7:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { Response } from "./response.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/cookies.ts:8:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { Context } from "./context.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/send.ts:6:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { Application } from "./application.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/server_sent_event.ts:3:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { ServerRequest } from "./types.d.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/server_sent_event.ts:5:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { Application, State } from "./application.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/context.ts:3:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { KeyStack } from "./keyStack.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/context.ts:11:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { ErrorStatus, ServerRequest } from "./types.d.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/context.ts:19:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { State } from "./application.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/middleware.ts:5:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { Context } from "./context.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/middleware.ts:6:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import {
^
    at https://deno.land/x/oak@v6.1.0/application.ts:12:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { State } from "./application.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/router.ts:28:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { Context } from "./context.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/router.ts:29:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { HTTPMethods, RedirectStatus } from "./types.d.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/router.ts:42:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { Context } from "./context.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/helpers.ts:3:1

TS1371 [ERROR]: This import is never used as a value and must use 'import type' because the 'importsNotUsedAsValues' is set to 'error'.
import { RouterContext } from "./router.ts";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    at https://deno.land/x/oak@v6.1.0/helpers.ts:4:1

[kitsonk]

Closed by #244