Add pull request template

Most MeshCore PRs lack structured descriptions — testing info, hardware
verification, and related issue links are frequently missing. This adds a
compact PR template with summary, type of change, hardware tested, and
test plan sections to encourage consistent, reviewable submissions.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

.github/pull_request_template.md

@@ -0,0 +1,26 @@
+## Summary
+
+<!-- What does this PR do and why? Link to related issues with "Fixes #123". -->
+
+## Type of Change
+
+- [ ] Bug fix
+- [ ] New feature
+- [ ] Board / variant support
+- [ ] Breaking change
+- [ ] Build system / CI
+- [ ] Refactor / code quality
+- [ ] Documentation
+
+## Hardware Tested
+
+<!-- List the hardware you tested on, or "None" if you don't have hardware. -->
+<!-- e.g., T1000-E, Heltec LoRa32 v3, RAK4631, T-Deck -->
+
+## Test Plan
+
+<!-- How did you verify this change works? -->
+
+- [ ] Compiles without warnings on target environment(s): ___
+- [ ] Tested on physical hardware
+- [ ] Tested via companion app: ___