workflow: add request to rewrite the history

When commit history does not provide sufficient details for a reader, we might request updating the commit history.
This often happens for new functionality or changing the current one without explaining why are we changing it or
how to use a new one.

Good example that would lead to change request in the PR is "Initial version for new feature" one-liner in the commit history.

Author: 0xc0170

docs/reference/contributing/guidelines/workflow.md

@@ -64,6 +64,8 @@ Pull requests on GitHub have to meet the following requirements to keep the code
 - Comment in the pull request on every change (rebase or new commits). This helps reviewers to be up to date with changes
 - Pull requests should fix a bug, add a feature or refactor.
 
+If commits do not follow above guidelines, you might be requested to modify the commit history (it is often adding more details to address _what_ and _why_ vs _how_).
+
 #### Release versioning
 
 You can find Mbed OS versioning at [How We Release Arm Mbed OS](../introduction/how-we-release-arm-mbed-os.html).