PULL_REQUEST_TEMPLATE

## What does this PR do?

[//]: # (Required: Describe the effects of your pull request in detail. If
multiple changes are involved, a bulleted list is often useful.)

## What gif best describes this PR or how it makes you feel?

[//]: # (Encouraged: Insert an appropriate gif/meme to brighten up your reviewer's day.)

## Completion checklist

- [ ] Additions and changes have unit tests
- [ ] [Unit tests, Pylint, security testing, and Integration tests are passing.](https://github.com/salesforce/endgame/actions). GitHub actions does this automatically
- [ ] The pull request has been appropriately labeled using the provided PR labels