changelog: include migration steps and resolutions

This commit updates the `changelog` following the removal
of deprecated extensions from the repository.
The commit includes the following:
- A link for application developers to our wiki page for `migration` steps.
- Alternative use of `yarn resolutions`.

Signed-off-by: vince-fugnitto <[email protected]>

CHANGELOG.md

@@ -60,6 +60,16 @@ Breaking changes:
   - The extension will no longer be maintained by the project and remains in the Git history for anyone who would like to reference it or maintain it.
 - [typescript] removed the `@theia/typescript` extension [#6933](https://github.com/eclipse-theia/theia/pull/6933)
   - The extension will no longer be maintained by the project and remains in the Git history for anyone who would like to reference it or maintain it.
+- The release includes the removal of language-specific extensions which have been replaced by VS Code extensions.
+  - Migration steps are available at the following wiki page [`Consuming Builtin and External VS Code Extensions`](https://github.com/eclipse-theia/theia/wiki/Consuming-Builtin-and-External-VS-Code-Extensions).
+  - Alternatively, it is also possible to use [`yarn resolutions`](https://classic.yarnpkg.com/en/docs/selective-version-resolutions/) to keep using old native extensions.\
+    For example, in your application's `package.json`, you can include the following (to keep using `@theia/typescript` and `@theia/textmate-grammars`):
+    ```json
+    "resolutions": {
+        "@theia/typescript": "0.15.0",
+        "@theia/textmate-grammars": "0.15.0"
+    },
+    ```
 
 ## v0.15.0