add template (#190)

Author: JensOgorek

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,15 @@
+### Motivation
+
+<!-- What problem does this PR solve? Which new feature or improvement does it implement? -->
+<!-- Please provide relevant links to corresponding issues and feature requests. -->
+
+### Implementation
+
+<!-- What is the concept behind the implementation? How does it work? -->
+<!-- Include any important technical decisions or trade-offs made -->
+
+### Progress
+
+- [ ] The implementation is complete.
+- [ ] Tested on hardware (or is not necessary).
+- [ ] Documentation has been updated (or is not necessary).