ConfigSync development has moved to Github

[mikebz]

Hi everyone! After a few months of mirroring Google internal development to Github we have moved the primary development activity to Github. You will now be able to see the upcoming pull requests, potentially add your own fixes and features and participate in the discussion.

For information about contributing, please visit this doc:
https://github.com/GoogleContainerTools/kpt-config-sync/blob/main/docs/contributing.md

Thank you and we are looking forward to working together!