[template] update [ci skip]

.github/PULL_REQUEST_TEMPLATE

@@ -1,10 +1,11 @@
 <!-- Thanks for contributing to open-source-ios-apps 😊 -->
 
 <!-- When making an addition: -->
-1. [ ] Insert the project in alphabetical order
-2. [ ] Avoid iOS or open-source in description as it is assumed :-)
-3. [ ] Use this commit title format if applicable: Add app-name by @github-username
-4. [ ] Follow the following template (use 🔶 for Swift projects)
+1. [ ] One project per pull request
+2. [ ] Insert the project in alphabetical order
+3. [ ] Avoid iOS or open-source in description as it is assumed :-)
+4. [ ] Use this commit title format if applicable: Add app-name by @github-username
+5. [ ] Follow the following template (use 🔶 for Swift projects)
 
 <!-- 
   - App name: Short description 🔶