Elaborate on the Scala.js section according to @sjrd suggestion

Author: anatoliykmetyuk

docs/blog/_posts/2020-11-09-scala3-m1.md

@@ -16,7 +16,16 @@ Below, you can find a short summary of the changes that took place during betwee
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 # Scala.js support for Scala 3
-Implemented by PRs [#9774](https://github.com/lampepfl/dotty/pull/9774) and [#9725](https://github.com/lampepfl/dotty/pull/9725), Scala 3 now supports Scala.js. You can read more about this in the [official announcement](https://www.scala-lang.org/2020/11/03/scalajs-for-scala-3.html).
+Dotty 0.27.0-RC1 had introduced preliminary Scala.js support with the portable subset of Scala and native JavaScript types.
+Scala 3.0.0-M1 significantly expands on that support:
+
+* support for non-native JS types ([#9774](https://github.com/lampepfl/dotty/pull/9774)), and
+* better support for other JS interop features, notably their interactions with Scala 3 features such as top-level declarations and `enum`s (e.g, [#9725](https://github.com/lampepfl/dotty/pull/9725) and [#9955](https://github.com/lampepfl/dotty/pull/9955)).
+
+The only remaining feature of Scala.js that is not supported yet is JS exports: `@JSExport` and its siblings `@JSExportAll`, `@JSExportTopLevel` and `@JSExportStatic` are all ignored by Scala 3.0.0-M1.
+Support for JS exports will come in the next release.
+
+For related reading, you can learn more on what it took to [implement Scala.js support in Scala 3 on our blog](https://www.scala-lang.org/2020/11/03/scalajs-for-scala-3.html).
 
 # Allow `as` in place of `@` for pattern bindings
 As the title suggests, this change is fairly straightforward. Now, instead of: