docs: add pull request template

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,22 @@
+<!--- Provide a general summary of your changes in the title above -->
+
+## Types of changes
+<!--- What types of changes does your code introduce? Put an `x` in all the boxes that apply: -->
+- [ ] Bug fix (a non-breaking change which fixes an issue)
+- [ ] New feature (a non-breaking change which adds functionality)
+- [ ] Breaking change (fix or feature that would cause existing functionality to change)
+
+
+## Description
+<!--- Describe your changes in detail -->
+<!--- Why is this change required? What problem does it solve? -->
+<!--- If it resolves an open issue, please link to the issue here. For example "Resolves: #137" -->
+
+
+## Checklist:
+<!--- Put an `x` in all the boxes that apply. -->
+<!--- If your change requires a documentation PR, please link it appropriately -->
+<!--- If you're unsure about any of these, don't hesitate to ask. We're here to help! -->
+- [ ] My change requires a change to the documentation.
+- [ ] I have updated the documentation accordingly.
+- [ ] I have added tests to cover my changes (if not applicable, please state why)