first add

docs/contributing.md

@@ -0,0 +1,31 @@
+# How to Contribute
+
+We welcome small patches related to bug fixes and documentation, but we do not
+plan to make any major changes to this repository.
+
+## Before You Begin
+
+### Sign Our Contributor License Agreement
+
+Contributions to this project must be accompanied by a
+[Contributor License Agreement](https://cla.developers.google.com/about) (CLA).
+You (or your employer) retain the copyright to your contribution; this simply
+gives us permission to use and redistribute your contributions as part of the
+project.
+
+If you or your current employer have already signed the Google CLA (even if it
+was for a different project), you probably don't need to do it again.
+
+Visit <https://cla.developers.google.com/> to see your current agreements or to
+sign a new one.
+
+### Review Our Community Guidelines
+
+This project follows
+[Google's Open Source Community Guidelines](https://opensource.google/conduct/).
+
+## Contribution Process
+
+We won't accept pull requests directly, but if you send one, we will review it.
+If we send a fix based on your pull request, we will make sure to credit you in
+the release notes.