chore(GitHub): add PR template

PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,23 @@
+<!---
+What types of changes does your code introduce? Put an `x` in all the boxes that apply:
+-->
+- [ ] Bug fix <!-- (change which fixes an issue) -->
+- [ ] New feature <!-- (change which adds functionality) -->
+- [ ] Chore <!-- (change which doesn't affect the usage of the package (such as a documentation, build process, or project setup change)) -->
+- [ ] Breaking change <!-- (fix or feature that would cause existing functionality to change) -->
+- [ ] There is an open issue which this change addresses
+- [ ] I have read the **[CONTRIBUTING](./CONTRIBUTING.md)** document.
+- [ ] My commits follow the [Git Commit Guidelines](https://github.com/angular/angular.js/blob/master/DEVELOPERS.md#commits)
+- [ ] My code follows the code style of this project.
+- [ ] My change requires a change to the documentation.
+- - [ ] I have updated the documentation accordingly.
+- [ ] I have added tests to cover my changes.
+- [ ] All new and existing tests passed.
+
+<!-- Put any other information you believe would be useful to know when reviewing this PR below -->
+
+
+<!---
+If there is an issue this PR addresses, please make sure it is in the commit message per the Git Commit Guidelines above 
+**AND** put the issue number below, indicating that is closes or fixes the issue.
+-->