chore: add PR template

.github/PULL_REQUEST_TEMPLATE.md

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+## Related Issue
+
+<!-- Link related issue -->
+
+## Description
+
+<!-- Describe what this PR changes. -->
+
+## Review Procedure
+
+<!-- Explain how to review this PR. -->
+
+## Related PR(optional)
+
+<!-- Link related PR -->
+
+## Remarks(optional)
+
+<!-- Write remarks as you like if you need them. -->
+
+## Pre-Review Checklist for the PR Author
+
+**PR Author should check the checkboxes below when creating the PR.**
+
+- [ ] Check documentation
+- [ ] Check sample files
+- [ ] Read [commit-guidelines][commit-guidelines]
+- [ ] Assign PR to reviewer
+
+## Checklist for the PR Reviewer
+
+**Reviewers should check the checkboxes below before approval.**
+
+- [ ] Commits are properly organized and messages are according to the guideline
+- [ ] (Optional) Unit tests have been written for new behavior
+- [ ] PR title describes the changes
+
+## Post-Review Checklist for the PR Author
+
+**PR Author should check the checkboxes below before merging.**
+
+- [ ] All open points are addressed and tracked via issues or tickets
+
+## CI Checks
+
+- **Build and test for PR / build-and-test-pr**: Required to pass before the merge.
+- **Build and test for PR / clang-tidy-pr**: NOT required to pass before the merge. It is up to the reviewer(s). Found false positives? See the [guidelines][clang-tidy-guidelines].
+- **Check spelling**: NOT required to pass before the merge. It is up to the reviewer(s). See [here][spell-check-dict] if you want to add some words to the spell check dictionary.
+
+[commit-guidelines]: https://www.conventionalcommits.org/en/v1.0.0/
+[spell-check-dict]: https://github.com/tier4/autoware-spell-check-dict#how-to-contribute