Add CONTRIBUTING.md

Author: hashhar

.github/CONTRIBUTING.md

@@ -0,0 +1,9 @@
+# Contributing to Trino Python Client
+
+## Contributor License Agreement ("CLA")
+
+In order to accept your pull request, we need you to [submit a CLA](https://github.com/trinodb/cla).
+
+## License
+
+By contributing to Trino Python Client, you agree that your contributions will be licensed under the [Apache License Version 2.0 (APLv2)](../LICENSE).

README.md

@@ -12,6 +12,8 @@ It supports Python>=3.7 and pypy.
 See [DEVELOPMENT](.github/DEVELOPMENT.md) for information about code style,
 development process, and guidelines.
 
+See [CONTRIBUTING](.github/CONTRIBUTING.md) for contribution requirements.
+
 ## Usage
 
 ### The Python Database API (DBAPI)