Add PR template

Author: nfhipona

.github/pull_request_template.md

@@ -0,0 +1,28 @@
+<!--- Provide a general summary of your changes -->
+
+## Description
+
+<!--- Describe your changes in detail -->
+
+## Motivation and Context
+
+<!--- Why is this change required? What problem does it solve? -->
+
+## Validation
+
+<!--- 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. -->
+
+## Screenshots (if appropriate)
+
+<!--- supporting screenshots. -->
+
+## 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)
+- [ ] Improvement (non-breaking change which enhances existing functionalities)
+- [ ] Breaking change (fix or feature that would cause existing functionality or the API to change)