Add pull request template

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,15 @@
+## Description
+
+*Please explain here what feature or bugfix these changes are addressing and why they should be included*
+
+## All submissions
+
+* [ ] there are no other open [Pull Requests](../../../pulls) for the same update/change
+* [ ] Bromite can be built with these changes
+* [ ] I have tested that the new change works as intended (AVD or physical device will do)
+
+### Format
+
+* [ ] patch subject and filename match (e.g. `Subject: Alternative cache (NIK-based)` -> `Alternative-cache-NIK-based.patch`)
+* [ ] patch description contains explanation of changes
+* [ ] no unnecessary whitespace or unrelated changes