Update API overview page (#791)

Author: cknitt

pages/docs/manual/latest/api.mdx

@@ -1,21 +1,18 @@
 # Overview
 
-## New Standard Library
+## ReScript Core
 
-[ReScript Core](api/core) is ReScript's new standard library. It replaces the complete `Js` module as well as some of the more frequently used modules from `Belt` and is recommended to use with uncurried mode.
+[Core](api/core) is ReScript's new standard library. It replaces the complete `Js` module as well as some of the more frequently used modules from `Belt` and is recommended to use with uncurried mode.
 
-## Other Modules
+In ReScript 11, it is shipped as a separate npm package `@rescript/core` that is added to your project as per the [installation instructions](http://localhost:3000/docs/manual/latest/installation). In future ReScript versions, it will be included with the `rescript` npm package itself.
 
-ReScript ships 3 modules in its standard library.
+## Additional Libraries
 
-- [Js](api/js): bindings for all your familiar JavaScript APIs.
-- [Belt](api/belt): extra collections and helpers not available in JavaScript.
-- [Dom](api/dom): Dom related types and modules.
+ReScript ships with these two additional modules in its standard library:
 
-Usage heuristics:
+- [Belt](api/belt): immutable collections and extra helpers not available in JavaScript / [Core](api/core).
+- [Dom](api/dom): Dom related types and modules. Contains our standardized types used by various userland DOM bindings.
 
-- Default to using the `Js` module. Most of the APIs in it are runtime-free and compile down to clean, readable JavaScript, which is our priority.
-- For other APIs that aren't available in regular JavaScript (and thus don't exist in our `Js` bindings), use Belt. For example, prefer `Js.Array2` over `Belt.Array`.
-- The `Dom` module contains our standardized types used by various userland DOM bindings. Due to the complexity of DOM, we don't mind that you ignore this module and build your application-specific DOM bindings.
+## Legacy Modules
 
-**Note**: we do not recommend other userland standard library alternatives (unless it's DOM bindings). These cause confusion and split points for the community.
+The [Js](api/js) module is superseded by [Core](api/core).