chore: add PR template (#11027)

Author: Splaktar

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,43 @@
+## PR Checklist
+Please check that your PR fulfills the following requirements:
+
+- [ ] The commit message follows [our guidelines](https://github.com/angular/material/blob/master/.github/CONTRIBUTING.md#-commit-message-format)
+- [ ] Tests for the changes have been added (for bug fixes / features)
+- [ ] Docs have been added / updated (for bug fixes / features)
+
+
+## PR Type
+What kind of change does this PR introduce?
+
+<!-- Please check the one that applies to this PR using "x". -->
+```
+[ ] Bugfix
+[ ] Feature
+[ ] Code style update (formatting, local variables)
+[ ] Refactoring (no functional changes, no api changes)
+[ ] Build related changes
+[ ] CI related changes
+[ ] Documentation content changes
+[ ] Infrastructure changes
+[ ] Other... Please describe:
+```
+
+## What is the current behavior?
+<!-- Please describe the current behavior that you are modifying and link to a relevant issue. -->
+
+Issue Number: 
+
+
+## What is the new behavior?
+
+
+## Does this PR introduce a breaking change?
+```
+[ ] Yes
+[ ] No
+```
+
+<!-- If this PR contains a breaking change, please describe the impact and migration path for existing applications below. -->
+<!-- Note that breaking changes are highly unlikely to get merged to master unless the validation is clear and the use case is critical. -->
+
+## Other information