Add CONTRIBUTING.md file


Point potential contributors to contribute.qt-project.org.

Change-Id: I774edafe66c013a06577a297b136d252fad6f208
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
commit3a9bf60d0c95750da09cd862702bce0b61ee269c
parent014918fa156d021c051d56126b0f240cd631c02f
authorKai Köhne <kai.koehne@qt.io>
committerKai Köhne <kai.koehne@qt.io>
commit timeFri, 17 Apr 2026 06:32:05 +0000