Create CONTRIBUTING.md

Author: hasanbayatme

CONTRIBUTING.md

@@ -0,0 +1,30 @@
+# Contribution Guidelines
+
+:clap: :tada: First off all thanks for contributing to us :tada: :clap:
+
+## What we do?
+
+We take release notes from [unity official release archive](https://unity3d.com/unity/get-unity/archive) and 
+then we file them here for better search functionally using GitHub search.
+
+You can choose one the below ways to contribute.
+
+## Adding Release Notes
+
+You can find missing release note from [unity official release archive](https://unity3d.com/unity/get-unity/archive) and add them to their 
+related folder.
+
+For example: If you found 1.0 or 1.0.0 is missing you should create **1.0** folder then add **1.0.0.txt** file to the folder and 
+put the release notes the file.
+
+## Fixing Release Notes
+
+You can fix existing release notes, for example sometimes the release notes contains grammer and missing content so you find them and fix them.
+
+## Suggesting Release Notes
+
+Don't have time to add a release note yourself? [:postbox: Send it to us](https://github.com/UnityCommunity/UnityReleaseNotes/issues) and then we will add it as soon as possible.
+
+Thanks.
+
+Made with :heart: by [Unity Community](https://github.com/UnityCommunity/)