Update CONTRIBUTING.md (#2779)

* Update CONTRIBUTING.md

@Cool-Katt something like this for now?

* [CI] Format code

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Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: SleeplessByte

CONTRIBUTING.md

@@ -4,6 +4,13 @@ This is the JavaScript track, one of the many tracks on [exercism][web-exercism]
 You can find this in the [`config.json`][file-config].
 It's not uncommon that people discover incorrect implementations of certain tests, have a suggestion for a track-specific hint to aid the student on the _JavaScript specifics_, see optimisations in terms of the configurations of `jest`, `eslint` or other dependencies, report missing edge cases, factual errors, logical errors, and, implement exercises or develop new exercises.
 
+> [!CAUTION]
+>
+> Please see https://github.com/exercism/javascript/issues/2144.
+>
+> All contributions _MUST_ preceed by opening a topic on the forum.
+> This is for both new content and fixes/changes to old content.
+
 We welcome contributions of all sorts and sizes, from reporting issues to submitting patches, as well as joining the current [discussions 💬][issue-discussion].
 
 > [!WARNING]
@@ -112,6 +119,9 @@ Don't worry! You're not alone in this.
 
 There are always improvements possible on existing exercises.
 
+> [!IMPORTANT]  
+> If you are opening a PR, please ensure you are _on a branch in your fork_, or our automated tooling will not work as expected.
+
 #### Improving the README.md
 
 For _practice_ exercises, `README.md` is generated from a canonical source.