feat: add pull request template

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,34 @@
+## Description
+<!--- Describe your changes in detail -->
+
+## Motivation and Context
+<!--- Why is this change required? What problem does it solve? -->
+
+## How Has This Been Tested?
+<!--- Please describe in detail how you tested your changes. -->
+<!--- Include details of your testing environment, and the tests you ran to -->
+<!--- see how your change affects other areas of the code, etc. -->
+- test environment:
+- test case 1:
+- test case 2:
+- ...
+
+## Screenshots (if appropriate):
+
+## Types of changes
+<!--- What types of changes does your code introduce? Put an `x` in all the boxes that apply: -->
+- [ ] Bug fix (non-breaking change which fixes an issue)
+- [ ] New feature (non-breaking change which adds functionality)
+- [ ] Database schema changes (next release will require increase of minor version instead of patch)
+- [ ] Breaking change (fix or feature that would cause existing functionality to change)
+- [ ] Technical debt
+- [ ] Tests only (no source changes)
+
+## Checklist:
+<!-- Tick the checkboxes when done. -->
+<!-- Raise documentation ticket in https://github.com/owncloud/documentation -->
+- [ ] Code changes
+- [ ] Unit tests added
+- [ ] Acceptance tests added
+- [ ] Documentation ticket raised: <link> 
+- [ ] Changelog item, see [TEMPLATE](https://github.com/owncloud/client/blob/master/changelog/TEMPLATE)