Add GitHub pull request template (#1581)

Co-authored-by: William Easton <strawgate@users.noreply.github.com>
Co-authored-by: marvin-context-protocol[bot] <225465937+marvin-context-protocol[bot]@users.noreply.github.com>

.github/pull_request_template.md

@@ -0,0 +1,28 @@
+## Description
+<!-- 
+Please provide a clear and concise description of the changes made in this pull request.
+
+Using AI to generate code? Please include a note in the description with which AI tool you used.
+-->
+
+**Contributors Checklist**
+<!--
+NOTE:
+1. You must create an issue in the repository before making a Pull Request.
+2. You must not create a Pull Request for an issue that is already assigned to someone else.
+
+If you do not follow these steps, your Pull Request will be closed without review.
+-->
+
+- [ ] My change is related to issue #(issue number)
+- [ ] I have followed the repository's development workflow
+- [ ] I have tested my changes manually and by adding relevant tests
+- [ ] I have performed all required documentation updates
+
+**Review Checklist**
+<!-- Your Pull Request will not be reviewed if tests are failing, you have not self-reviewed your changes, or you have not checked all of the following: -->
+
+- [ ] I have self-reviewed my changes
+- [ ] My Pull Request is ready for review
+
+---