Add templates for github issues & pull requests

re: #1763
based on: #1764

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,19 @@
+**Checklist**
+
+- [ ] I have read the [Contribution & Best practices Guide](https://github.com/openSUSE/osem/blob/master/CONTRIBUTING.md).
+- [ ] My branch is up-to-date with the upstream `master` branch.
+- [ ] The tests pass locally with my changes.
+- [ ] I have added tests that prove my fix is effective or that my feature works(if appropriate).
+- [ ] I have added necessary documentation (if appropriate).
+
+**Short description of what this resolves/which [issues](https://github.com/openSUSE/osem/issues) does this fix?:**
+
+<!-- List the issue number resolved with this change; if there is no open issue, describe the problem this request solves -->
+
+-
+
+**Changes proposed in this pull request:**
+
+<!-- Summarize the changes, using declarative language. -->
+
+-