Update contribution guidelines for 1 PR per change

Author: dhamaniasad

CONTRIBUTING.md

@@ -2,8 +2,8 @@ This list [accepts and encourages pull requests](https://github.com/dhamaniasad/
 
 # Contribution Guidelines
 
-- **To add to the list:** Submit a pull request to [README.md](https://github.com/dhamaniasad/awesome-postgres/blob/master/README.md), optionally add comment if you wish to elaborate/explain.
-- **To edit an item:** Submit a pull request to [README.md](https://github.com/dhamaniasad/awesome-postgres/blob/master/README.md), add comment explaining the reasoning behind the change.
+- **To add to the list:** Submit a pull request to [README.md](https://github.com/dhamaniasad/awesome-postgres/blob/master/README.md), optionally add comment if you wish to elaborate/explain. One pull request for one item.
+- **To edit an item:** Submit a pull request to [README.md](https://github.com/dhamaniasad/awesome-postgres/blob/master/README.md), add comment explaining the reasoning behind the change. One pull request for change to one item.
 - **To remove from the list:** Open an issue
 
 You may add, edit, or request to remove: