📝 docs(CONTRIBUTING.md): Update contribution guidelines due to change in project maintenance

The contribution guidelines have been updated to reflect the recent changes in the project's maintenance. As of September 15th, 2023, Mattermost, Inc. staff are no longer reviewing or merging pull requests for either Focalboard or the Mattermost Boards plugin in this repository. The community is encouraged to fork this repository for continued development and contributions. This change is due to Mattermost's decision to focus developer resources on improving the platform’s performance and core features. The list of contributors has been updated to 'Past maintainers'.

CONTRIBUTING.md

@@ -1,47 +1,20 @@
-# Code Contribution Guidelines
+# Disclaimer
 
-Thank you for your interest in contributing! Please read the [Focalboard Contribution Guide](https://developers.mattermost.com/contribute/focalboard/) to learn the process for making code contributions, and [join our Focalboard community channel](https://community.mattermost.com/core/channels/focalboard) to get help from community members and the core team.
+> [!WARNING]
+> **Effective September 15th, 2023, Mattermost, Inc. staff are no longer reviewing or merging pull requests for either Focalboard or the Mattermost Boards plugin in this repository (`mattermost/focalboard`). We encourage the community to fork this repository for continued development and contributions.**
+>
+> The reason behind these changes is to focus Mattermost developer resources on improving the platform’s performance and core features to ensure Mattermost continues being resilient, stable, and best-in-breed for critical operations.
+>
+> ️💡 [Learn more](https://forum.mattermost.com/t/upcoming-product-changes-to-boards-and-various-plugins/16669)
 
-When you submit a pull request, it goes through a code review process outlined [here](https://developers.mattermost.com/contribute/getting-started/code-review/).
+## Past maintainers
 
-After a noteable bug fix or improvement is merged, submit a pull request to the [CHANGELOG](CHANGELOG.md) under the next release section.
-
-## Bug Reports
-
-Please file a [GitHub issue](https://github.com/mattermost/focalboard/issues) if anything isn't working the way you expect.
-
-## Documentation
-
-You can contribute to the [Mattermost Boards documentation](https://docs.mattermost.com/guides/boards.html). Read more about how the contribution process works in the repository's [README](https://github.com/mattermost/docs/blob/master/README.md). Visit the [Documentation Working Group channel](https://community.mattermost.com/core/channels/dwg-documentation-working-group) on our community server if you have any questions!
-
-## Contributors
-
-**Core Committers**: Maintains the Focalboard project and has merge access to the repositories. They are responsible for reviewing pull requests, cultivating the developer community, and guiding the technical vision of Focalboard. If you have a question or need some help, these are the people to ask.
-
-- **<a name="scott.bishel">Scott Bishel</a>**
-    - @scott.bishel on [community.mattermost.com](https://community.mattermost.com/core/messages/@scott.bishel) and [@sbishel](https://github.com/sbishel) on GitHub
-- **<a name="jesús.espino">Jesús Espino</a>**
-    - @jesus.espino on [community.mattermost.com](https://community.mattermost.com/core/messages/@jesus.espino) and [@jespino](https://github.com/jespino) on GitHub
-- **<a name="doug.lauder">Doug Lauder</a>**
-    - @doug.lauder on [community.mattermost.com](https://community.mattermost.com/core/messages/@doug.lauder) and [@wiggin77](https://github.com/wiggin77) on GitHub
-- **<a name="miguel.delacruz">Miguel de la Cruz</a>**
-    - @miguel.delacruz on [community.mattermost.com](https://community.mattermost.com/core/messages/@miguel.delacruz) and [@mgdelacroix](https://github.com/mgdelacroix) on GitHub
-- **<a name="harshil.sharma">Harshil Sharma</a>**
-    - @harshil.sharma on [community.mattermost.com](https://community.mattermost.com/core/messages/@harshil.sharma) and [@harshilsharma63](https://github.com/harshilsharma63) on GitHub
-- **<a name="chen.lim">Chen Lim</a>**
-    - @chen-i.lim on [community.mattermost.com](https://community.mattermost.com/core/messages/@chen-i.lim) and [@chenilim](https://github.com/chenilim) on GitHub
-
-**Quality Assurance**: Checks quality of code and verifies bug fixes.
-
-- **<a name="ogi.marusic">Ogi Marušić</a>**
-    - @ogi.marusic on [community.mattermost.com](https://community.mattermost.com/core/messages/@ogi.marusic) and [@ogi-m](https://github.com/ogi-m) on GitHub
-
-**Community Organizers**: Responds with comments to bug reports, issues, and pull requests with tags, edits and mentions to core committers and contributors.
-
-- **<a name="winson.wu">Winson Wu</a>**
-    - @winson.wu on [community.mattermost.com](https://community.mattermost.com/core/messages/@winson.wu) and [@wuwinson](https://github.com/wuwinson) on GitHub
-
-**Documentation**: Verifies documentation changes and updates documentation for new features.
-
-- **<a name="justine.geffen">Justine Geffen</a>**
-    - @justine.geffen on [community.mattermost.com](https://community.mattermost.com/core/messages/@justine.geffen) and [@justinegeffen ](https://github.com/justinegeffen) on GitHub
+- **Scott Bishel**: [@sbishel](https://github.com/sbishel)
+- **Jesús Espino**: [@jespino](https://github.com/jespino)
+- **Doug Lauder**: [@wiggin77](https://github.com/wiggin77)
+- **Miguel de la Cruz**: [@mgdelacroix](https://github.com/mgdelacroix)
+- **Harshil Sharma**: [@harshilsharma63](https://github.com/harshilsharma63)
+- **Chen Lim**: [@chenilim](https://github.com/chenilim)
+- **Ogi Marušić**: [@ogi-m](https://github.com/ogi-m)
+- **Winson Wu**: [@wuwinson](https://github.com/wuwinson)
+- **Justine Geffen**: [@justinegeffen](https://github.com/justinegeffen)