PYTHON-5580: Add pull request template (#213)

[PYTHON-5580](https://jira.mongodb.org/browse/PYTHON-5580)

## Summary
<!-- What is this PR introducing? If context is already provided from
the JIRA ticket, still place it in the Pull Request as you should not
make the reviewer do digging for a basic summary. -->

Adds a Pull Request template to this repository based on our new
dbx-python code review policy.

## Changes in this PR

<!-- What changes did you make to the code? What new APIs (public or
private) were added, removed, or edited to generate the desired outcome
explained in the above summary? -->

* PULL_REQUEST_TEMPLATE.md

## Test Plan

<!-- How did you test the code? If you added unit tests, you can say
that. If you didn’t introduce unit tests, explain why. All code should
be tested in some way – so please list what your validation strategy
was. -->

Make a PR from this branch to confirm

### Screenshots (optional)

<!-- Usually a great supplement to a test plan, especially if this
requires local testing. -->

## Checklist

<!-- Do not delete the items provided on this checklist -->

### Checklist for Author

- [x] Did you update the changelog (if necessary)?   **Not necessary**
- [x] Is the intention of the code captured in relevant tests? **Not
necessary**
- [x] If there are new TODOs, has a related JIRA ticket been created?
**Not necessary**

### Checklist for Reviewer [@caseyclements, @blink1073]

- [x] Does the title of the PR reference a JIRA Ticket?  
- [x] Do you fully understand the implementation? (Would you be
comfortable explaining how this code works to someone else?)
- [x] Have you checked for spelling & grammar errors?  
- [x] Is all relevant documentation (README or docstring) updated?

## Focus Areas for Reviewer

<!-- List any complex portion of code you believe needs additional
scrutiny and explain why. -->

For reviewers provide suggestions on what should be changed about the
checklist to better cater to this repository.

---------

Co-authored-by: Steven Silvester <steve.silvester@mongodb.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: 3 people

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,39 @@
+[Issue Key](https://jira.mongodb.org/browse/{ISSUE_KEY})
+
+## Summary
+
+<!-- What is this PR introducing? If context is already provided from the JIRA ticket, still place it in the Pull Request as you should not make the reviewer do digging for a basic summary. -->
+
+## Changes in this PR
+
+<!-- What changes did you make to the code? What new APIs (public or private) were added, removed, or edited to generate the desired outcome explained in the above summary? -->
+
+## Test Plan
+
+<!-- How did you test the code? If you added unit tests, you can say that. If you didn’t introduce unit tests, explain why. All code should be tested in some way – so please list what your validation strategy was. -->
+
+### Screenshots (optional)
+
+<!-- Usually a great supplement to a test plan, especially if this requires local testing. -->
+
+## Checklist
+
+<!-- Do not delete the items provided on this checklist -->
+
+### Checklist for Author
+
+- [ ] Did you update the changelog (if necessary)?
+- [ ] Is the intention of the code captured in relevant tests?
+- [ ] If there are new TODOs, has a related JIRA ticket been created?
+- [ ] Has a MongoDB Employee run [the patch build of this PR](https://github.com/mongodb-labs/ai-ml-pipeline-testing?tab=readme-ov-file#running-a-patch-build-of-a-given-pr)?
+
+### Checklist for Reviewer {@primary_reviewer}
+
+- [ ] Does the title of the PR reference a JIRA Ticket?
+- [ ] Do you fully understand the implementation? (Would you be comfortable explaining how this code works to someone else?)
+- [ ] Have you checked for spelling & grammar errors?
+- [ ] Is all relevant documentation (README or docstring) updated?
+
+## Focus Areas for Reviewer (optional)
+
+<!-- List any complex portion of code you believe needs particular scrutiny and explain why.  -->