Add CONTRIBUTING.md file

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

Change-Id: Id4dbc0dda57fe316f5d338dd0ef407b278287671
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

CONTRIBUTING.md

@@ -0,0 +1,11 @@
+## Qt contribution guidelines
+
+We welcome contributions to Qt!
+
+Note that we cannot accept pull requests on GitHub. All contributions
+to the Qt project are exclusively handled through the
+[Gerrit code review system](https://codereview.qt-project.org).
+
+See
+[contribute.qt-project.org](https://contribute.qt-project.org/) to learn
+more.

REUSE.toml

@@ -22,7 +22,8 @@ SPDX-FileCopyrightText = "Copyright (C) The Qt Company Ltd."
 SPDX-License-Identifier = "LicenseRef-Qt-Commercial OR BSD-3-Clause"
 
 [[annotations]]
-path = ["**.qdocconf",  "src/mqtt/doc/style/style.css", "tests/README.txt"]
+path = ["**.qdocconf",  "src/mqtt/doc/style/style.css",
+        "tests/README.txt", "CONTRIBUTING.md"]
 comment = "documentation"
 precedence = "closest"
 SPDX-FileCopyrightText = "Copyright (C) The Qt Company Ltd."

licenseRule.json

@@ -56,9 +56,10 @@
         }
     },
     {
-        "comment": "Files with the following endings are Documentation licensed.",
-        "file_pattern_ending": [".qdoc", ".qdocinc" , ".qdocconf", "README", "qt_attribution.json",
-                                 ".css", "README.txt"],
+        "comment": "Files with the following endings are documentation licensed.",
+        "file_pattern_ending": [".qdoc", ".qdocinc" , ".qdocconf", ".css",
+                                "README.txt", "CONTRIBUTING.md",
+                                "qt_attribution.json"],
         "location":{
             "": {
                 "comment": "",