GITHUB: add PR template (#3)

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,23 @@
+<!--- Provide a general summary of your changes in the Title above -->
+## Description
+<!--- Describe your changes in detail -->
+
+## Motivation and Context
+<!--- Why is this change required? What problem does it solve? -->
+<!--- If it fixes an open issue, please link to the issue here. -->
+
+## 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. -->
+
+## Where Has This Been Documented?
+<!--  Include where the changes made have been documented. -->
+<!--  This can simply be  a comment in the code or updating a docstring -->
+
+## Pre-merge checklist
+- [ ] Code works interactively
+- [ ] Code contains descriptive comments
+- [ ] Test suite passes locally
+- [ ] Libraries are set to ``Always Newest`` version (``Library, *``)
+- [ ] Committed with ``pre-commit`` or ran ``pre-commit run --all-files``