Merge pull request #2605 from nextcloud/addPullRequestTemplate

add initial pull request template for github

.github/pull_request_template.md

@@ -0,0 +1,18 @@
+### 🖼️ Screenshots
+
+🏚️ Before | 🏡 After
+---|---
+B | A
+
+
+### 🚧 TODO
+
+- [ ] ...
+
+### 🏁 Checklist
+
+- [ ] ⛑️ Tests (unit and/or integration) are included or not needed
+- [ ] 🔖 Capability is checked or not needed 
+- [ ] 🔙 Backport requests are created or not needed: `/backport to stable-xx.x`
+- [ ] 📅 Milestone is set
+- [ ] 🌸 PR title is meaningful (if it should be in the changelog: is it meaningful to users?)