PULL_REQUEST_TEMPLATE

<!--- Provide a general summary of your changes in the Title above -->
<!--- DELETE ALL COMMENTS BEFORE CREATING PULL REQUEST -->

## Description
<!--- Describe your changes in detail -->

## Related Issue
<!--- This project only accepts pull requests related to open issues -->
<!--- If suggesting a new feature or change, please discuss it in an issue first -->
<!--- If fixing a bug, there should be an issue describing it with steps to reproduce -->
<!--- Please link to the issue here: -->

## Motivation and Context
<!--- Why is this change required? What problem does it solve? -->

## How Can This Be Tested?
<!--- Please describe in detail how teammates can test your changes. -->

## 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)
- [ ] Breaking change (fix or feature that would cause existing functionality to change)