add pr template.

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,45 @@
+## Description
+
+What does this PR do? Provide a brief summary of the changes. 
+
+## Type of Change
+
+- [ ] Bug fix
+- [ ] New feature
+- [ ] Refactoring (no functional changes)
+- [ ] Documentation update
+- [ ] Other (please describe):
+
+## Checklist
+
+### Required for All PRs
+
+- [ ] Reproducible glTF test file(s) are included (e.g., `models/regression/`, `tests/issue-***.gltf`, etc.)
+- [ ] Unit tests are written and pass locally (`cd tests && ./tester`)
+
+### Required for Feature PRs
+
+- [ ] Specification document is included (e.g., `docs/spec/<feature-name>.md`)
+  - The spec should cover: purpose, API design, usage examples, and edge cases
+
+### Security Policy
+
+This project manages CVE assignments exclusively through GitHub Security Advisories.
+PRs that include or reference independently obtained CVE IDs or external vulnerability disclosures will be closed.
+
+## Test Instructions
+
+How can reviewers verify your changes? 
+
+```
+# Example:
+cd build && cmake .. && make test
+```
+
+## Related Issues
+
+Link related issues: 
+
+## Additional Notes
+
+Any other context, screenshots, or information relevant to the review.