chore: Add PR template (#81)

Signed-off-by: Michele Dolfi <[email protected]>

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,20 @@
+<!-- Thank you for contributing to Docling! -->
+
+<!-- STEPS TO FOLLOW:
+  1. Add a description of the changes (frequently the same as the commit description)
+  2. Enter the issue number next to "Resolves #" below (if there is no tracking issue resolved, **remove that section**)
+  3. Follow the steps in the checklist below, starting with the **Commit Message Formatting**.
+-->
+
+<!-- Uncomment this section with the issue number if an issue is being resolved
+**Issue resolved by this Pull Request:**
+Resolves #
+--->
+
+**Checklist:**
+
+- [ ] **Commit Message Formatting**: Commit titles and messages follow guidelines in the
+  [conventional commits](https://www.conventionalcommits.org/en/v1.0.0/#summary).
+- [ ] Documentation has been updated, if necessary.
+- [ ] Examples have been added, if necessary.
+- [ ] Tests have been added, if necessary.