GitHub: Add copy of README with GitHub mirror info

Pull Request: https://projects.blender.org/blender/blender/pulls/144539

.github/README.md

@@ -0,0 +1,42 @@
+<!--
+Keep this document short & concise,
+linking to external resources instead of including content in-line.
+See 'release/text/readme.html' for the end user read-me.
+-->
+
+> [!IMPORTANT]
+> Cloning from this [GitHub mirror](https://github.com/blender/blender) may cause Git LFS errors. To avoid this, use `GIT_LFS_SKIP_SMUDGE=1` when doing your initial clone.  
+> See [the documentation](https://developer.blender.org/docs/handbook/contributing/using_git/#github-mirror) for full instructions.
+
+Blender
+=======
+
+Blender is the free and open source 3D creation suite.
+It supports the entirety of the 3D pipeline—modeling, rigging, animation, simulation, rendering, compositing,
+motion tracking and video editing.
+
+![Blender screenshot](https://code.blender.org/wp-content/uploads/2018/12/springrg.jpg "Blender screenshot")
+
+Project Pages
+-------------
+
+- [Main Website](http://www.blender.org)
+- [Reference Manual](https://docs.blender.org/manual/en/latest/index.html)
+- [User Community](https://www.blender.org/community/)
+
+Development
+-----------
+
+- [Build Instructions](https://developer.blender.org/docs/handbook/building_blender/)
+- [Code Review & Bug Tracker](https://projects.blender.org)
+- [Developer Forum](https://devtalk.blender.org)
+- [Developer Documentation](https://developer.blender.org/docs/)
+
+
+License
+-------
+
+Blender as a whole is licensed under the GNU General Public License, Version 3.
+Individual files may have a different but compatible license.
+
+See [blender.org/about/license](https://www.blender.org/about/license) for details.