Create pull_request_template.md with contribution rules

Added a pull request template with guidelines for contributors.

Author: jaime-olivares

.github/pull_request_template.md

@@ -0,0 +1,20 @@
+## PR Checklist
+
+Before submitting this PR, please make sure you follow these rules:
+
+### Mandatory Rules:
+- **One topic per PR** — Do not mix unrelated changes (e.g. bug fix + refactoring + new feature).
+- **Do not rename** variables, properties, methods, or classes unless there is a very strong reason (and explain it).
+- **Do not change coding style** (indentation, braces, quotes, spacing, etc.).
+- Keep changes focused and minimal.
+
+### Other Guidelines:
+- Write clear commit messages.
+- Add tests when applicable.
+- Update documentation if needed.
+
+---
+
+**If your PR violates any of the mandatory rules above, it may be closed or require significant rework.**
+
+Thank you for contributing!