Add template for pull requests.

Signed-off-by: Pol Henarejos <pol.henarejos@cttc.es>

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,50 @@
+## Summary
+
+Describe in plain language what this PR does and why.
+
+- What problem does it solve?
+- Is it a bug fix, a new feature, a cleanup/refactor…?
+
+
+## Details / Impact
+
+Please include any relevant details:
+
+- Hardware / board(s) tested:
+- Firmware / commit/base version:
+- Security impact (if any):
+  - e.g. changes PIN handling, touches key storage, affects attestation, etc.
+- Behavior changes:
+  - e.g. new command, new API surface, different defaults, etc.
+
+
+## Testing
+
+How did you test this change?
+
+- Steps to reproduce / validate:
+- Expected vs actual results:
+- Any logs / traces (please remove secrets):
+
+
+## Licensing confirmation (required)
+
+By checking the box below, you confirm ALL of the following:
+
+- You are the author of this contribution, or you have the right to contribute it.
+- You have read `CONTRIBUTING.md`.
+- You agree that this contribution may be merged, used, modified, and redistributed:
+  - under the AGPLv3 Community Edition, **and**
+  - under any proprietary / commercial / Enterprise editions of this project,
+    now or in the future.
+- You understand that submitting this PR does not create any support obligation,
+  SLA, or guarantee of merge.
+
+**I confirm the above licensing terms:**
+
+- [ ] Yes, I agree
+
+
+## Anything else?
+
+Optional: mention known limitations, follow-ups, or if this is related to an existing Issue.