Automatically link work items from commits to pull requests created via az repos pr create

Hey everyone,

I have a request to make the azure-cli behave more like the Azure DevOps GUI does when it comes to pull requests. We have a blind colleague who would really appreciate this feature since the GUI is not really useable for him.
* When I link a work item to a git commit (e.g. via `git commit -am "472 Remove test file"`) in a feature branch and then create a pull request from this feature branch via the GUI, the pull request will automatically link the work item:
* Unfortunately, when I create a pull request via `az repos pr create`, the work items mentioned in commits are not automatically linked.

I hope someone could take a look at this, I'm very glad my blind colleague is so open to branch policies, pull requests and all the other stuff I'm introducing.

Cheers,
Robin

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* ID: 3324c35b-f381-8db4-b168-6f73e20c1f3e
* Version Independent ID: 7a3e8656-7741-8365-e56c-44056f034b31
* Content: [az repos pr](https://docs.microsoft.com/en-us/cli/azure/ext/azure-devops/repos/pr?view=azure-cli-latest)
* Content Source: [latest/docs-ref-autogen/ext/azure-devops/repos/pr.yml](https://github.com/MicrosoftDocs/azure-docs-cli/blob/master/latest/docs-ref-autogen/ext/azure-devops/repos/pr.yml)
* GitHub Login: @rloutlaw
* Microsoft Alias: **routlaw**