docs: information on new conventional commit format (#9573)

(cherry picked from commit 8bf9780)

.github/PULL_REQUEST_TEMPLATE.md

@@ -5,6 +5,7 @@ show completion. -->
 
 - [ ] Updated associated README.md.
 - [ ] Wrote appropriate unit tests.
+- [ ] Pull request title or commits are in [conventional commit format](https://www.conventionalcommits.org/en/v1.0.0/#summary) (e.g. feat: or fix:)
 
 <!-- Link to issues that describe the need for the change. Issues
 should include context that will help reviewers understand why the

CONTRIBUTING.md

@@ -1,17 +1,20 @@
 ### Contributing
 
 1. [Sign the CLA][cla].
-1. Open a [new issue][] to discuss the changes you would like to make.  This is
+2. Open a [new issue][] to discuss the changes you would like to make.  This is
    not strictly required but it may help reduce the amount of rework you need
    to do later.
-1. Make changes or write plugin using the guidelines in the following
+3. Make changes or write plugin using the guidelines in the following
    documents:
    - [Input Plugins][inputs]
    - [Processor Plugins][processors]
    - [Aggregator Plugins][aggregators]
    - [Output Plugins][outputs]
-1. Ensure you have added proper unit tests and documentation.
-1. Open a new [pull request][].
+4. Ensure you have added proper unit tests and documentation.
+5. Open a new [pull request][].
+6. The pull request title needs to follow [conventional commit format](https://www.conventionalcommits.org/en/v1.0.0/#summary)
+
+**Note:** If you have a pull request with only one commit, then that commit needs to follow the conventional commit format or the `Semantic Pull Request` check will fail. This is because github will use the pull request title if there are multiple commits, but if there is only one commit it will use it instead.
 
 #### Contributing an External Plugin *(new)*