doc(PULL_REQUEST_TEMPLATE): use checklist & comment

.github/PULL_REQUEST_TEMPLATE.yml

@@ -1,15 +1,13 @@
-# Pull Requests
+<!-- Please note that we accept pull requests from anyone, but that does not mean it will be merged. -->
-
-Please note that we accept pull requests from anyone, but that does not mean it will be merged.
 
 ## What kind of change does this PR introduce?
-* Fix
+- [ ] Fix
-* Feature
+- [ ] Feature
-* Codestyle
+- [ ] Codestyle
-* Refactor
+- [ ] Refactor
-* Other
+- [ ] Other
 
 ## Did this PR introduce a breaking change?
 _A breaking change includes anything that breaks backwards compatibility either at compile or run time._
-* Yes, please list breaking changes
+- [ ] Yes, please list breaking changes
-* No
+- [ ] No