openmct/.github/PULL_REQUEST_TEMPLATE.md

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Closes <!--- Insert Issue Number(s) this PR addresses. Start by typing # will open a dropdown of recent issues. Note: this does not work on PRs which target release branches -->

### Describe your changes:
<!--- Describe your changes and add any comments about your approach either here or inline if code comments aren't added -->

### All Submissions:

* [ ] Have you followed the guidelines in our [Contributing document](https://github.com/nasa/openmct/blob/master/CONTRIBUTING.md)?
* [ ] Have you checked to ensure there aren't other open [Pull Requests](https://github.com/nasa/openmct/pulls) for the same update/change?
* [ ] Is this a notable change that will require a special callout in the release notes [Notable Change](../docs/src/process/release.md) ? For example, will this break compatibility with existing APIs or projects which source these plugins?

### Author Checklist

* [ ] Changes address original issue?
* [ ] Tests included and/or updated with changes?
* [ ] Has this been smoke tested?
* [ ] Have you associated this PR with a `type:` label? Note: this is not necessarily the same as the original issue.
* [ ] Have you associated a milestone with this PR? Note: leave blank if unsure.
* [ ] Is this a breaking change to be called out in the release notes?
* [ ] Testing instructions included in associated issue OR is this a dependency/testcase change?

### Reviewer Checklist

* [ ] Changes appear to address issue?
* [ ] Reviewer has tested changes by following the provided instructions?
* [ ] Changes appear not to be breaking changes?
* [ ] Appropriate automated tests included?
* [ ] Code style and in-line documentation are appropriate?