chore(common): use a copyright + linter bot on PRs

Three things that belong together:

1. Use a linter bot to review code contributions for common issues on PRs.
2. Check header comment in all source files for copyright with a bot that runs on PRs.
3. Verify that hints and warnings in build logs are being tracked (currently, that is very project-dependent)

I propose that we fix source files over time rather than trying to fix them all at once.