chore: add PULL_REQUEST_TEMPLATE

Author: oli-hivemq

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,21 @@
+## Why
+
+<!-- Describe what this change is all about -->
+
+## What
+
+<!-- Describe your changes -->
+
+## Todos
+
+<!-- Please delete options that are not relevant -->
+
+- [ ] I have added a description to this pull request that describes the changes in detail
+- [ ] I have performed a self-review of my code
+- [ ] I have added a label that describes the PR type (`bug`, `enhancement`, `ci`, `refactor`, `documentation`, `test`, `chore`)
+- [ ] I have added `customer-facing 🙋‍♂️` label if this PR ships customer value
+- [ ] I have updated the _optional_ PR title to follow the pattern `Fix / TICKET_ID / DESCRIPTION` (e.g. `Fix / 123456 / Fixing the login button`)
+- [ ] I have run manual tests to check if everything is functional
+- [ ] I have added screenshots/videos that explain my graphical changes
+
+## Screenshots