Add PR template.

Author: robert-de-bock

.github/pull_request_template.md

@@ -0,0 +1,11 @@
+---
+name: Pull request
+about: Describe the proposed change
+
+---
+
+**Describe the change**
+A clear and concise description of what the pull request is.
+
+**Testing**
+In case a feature was added, how were tests performed?