Source Control supports app READMEs

READMEs can now be protected for apps that use Source Control. For existing apps that have a README, Retool will add a README.md file to your repository with your next commit. If you are protecting an app for the first time, Retool will include the README.md file automatically.

This feature is currently rolling out to cloud instances and will be available to self-hosted instances on an upcoming edge release.