Add CONTRIBUTING.md file


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

Change-Id: I3bb1a0f37b11a561b4df0bd3a4b07cb991da3e00
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
commit4fb295d3546e350dbf149da5ecbb91be9d01d9cd
parent9242ba2c099eb747e11cb70f6b334b3c7df0292c
authorKai Köhne <kai.koehne@qt.io>
committerKai Köhne <kai.koehne@qt.io>
commit timeWed, 22 Apr 2026 07:15:51 +0000