reduce the template to 5 checkable bullet points

.github/PULL_REQUEST_TEMPLATE.md

 
-## Description
-
-**Please provide a short abstract motivating your pull request.**
-
-
-## Breaking changes
-+ *list all breaking changes that this PR introduces*
-
-## Backwards-compatible changes
-+ *list all backwards-compatible changes that this PR introduces*
-
-## Details
-
-**For non-trivial PRs, please explain the background and implementation details.**
-
-## PR checklist
-+ [ ] are the changes covered by tests?
-+ [ ] re-run example notebooks if they are effected in a relevant way
-+ [ ] **mention the PR in the RELEASE-NOTES.md**
+**Thank your for opening a PR!**
+
+Depending on what your PR does, here are a few things you might want to address in the description:
++ [ ] what are the (breaking) changes that this PR makes?
++ [ ] important background, or a details about the implementation
++ [ ] are the changes covered by tests? 
++ [ ] are example-notebooks affected in a relevant way?
++ [ ] right before it's ready to merge, mention the PR in the RELEASE-NOTES.md