Change how type import/export specifiers are sorted

[lydell]

Closes #124.

Before – type specifiers come first:

import { type B, a } from "a";
export { type B, a } from "a";

After – all specifiers are sorted alphabetically, regardless of type:

import { a, type B } from "a";
export { a, type B } from "a";

Motivation:

You might import a class for a type annotation using:

import {
  type MyClass,
  coolFunction,
} from "example";

Later, you also start instantiating that class in the same file (new MyClass()), so you remove type.

Previously, this resulted in a messy diff due to the class moving:

 import {
-  type MyClass,
   coolFunction,
+  MyClass,
 } from "example";

Now it results in just the type keyword being removed:

 import {
-   type MyClass,
+   MyClass,
   coolFunction,
 } from "example";

This is consistent with https://github.com/lydell/eslint-plugin-simple-import-sort#why-sort-on-from