chore: import upstream snapshot with attribution

.github/PULL_REQUEST_TEMPLATE.md

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+## Summary
+<!-- What does this PR do? Keep it short (1-3 bullet points). -->
+
+-
+
+## Test plan
+<!-- How did you verify this works? -->
+
+- [ ] `cargo fmt --all && cargo clippy --all-targets && cargo test`
+- [ ] Manual testing: `rtk <command>` output inspected
+
+> **Important:** All PRs must target the `develop` branch (not `master`).
+> See [CONTRIBUTING.md](../blob/master/CONTRIBUTING.md) for details.