Add pull request template (#2843)

Author: superkhau

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,34 @@
+<!--
+See http://loopback.io/doc/en/contrib/triaging-pull-requests.html to understand
+the MINIMUM requirements for submitting pull requests.
+-->
+
+### Type of change
+
+<!--
+See http://semver.org/ for more info.
+-->
+
+- [ ] SEMVER-MAJOR -- Backwards-incompatible changes
+- [ ] SEMVER-MINOR -- Add functionality in a backwards-compatible manner
+- [ ] SEMVER-PATCH -- Backwards-compatible bug fixes
+
+### Description of change(s)
+
+
+
+### Link(s) to related GitHub issues
+
+
+
+### Checklist
+
+- [ ] CLA signed
+- [ ] Commit message conforms with the [Git commit message
+  guidelines](http://loopback.io/doc/en/contrib/git-commit-messages.html)
+- [ ] New tests are added to cover all changes
+- [ ] Code passes `npm test`
+- [ ] Code conforms with the [style
+  guide](http://loopback.io/doc/en/contrib/style-guide.html)
+- [ ] All CI builds are passing (semi-required, left up to discretion of the
+  reviewer)