Update CONTRIBUTING.md to reflect automated flow

Author: ochococo

CONTRIBUTING.md

@@ -3,6 +3,8 @@ How to contribute?
 
 - You are awesome!
 - Only editing files inside `source` is recommended, the rest is autogenerated and translated 
+- Commit changes
 - Run `generate-playground.sh` locally
-- Opene the .playground locally and check if it works
+- Open the .playground locally and check if it works
+- Remove the changes caused by `generate-playground.sh`, do not commit it! (_THIS IS A RECENT CHANGE_)
 - Please be patient and respectful to fellow contributors