enso/.github/PULL_REQUEST_TEMPLATE.md

### Pull Request Description
<!--
- Please describe the nature of your PR here, as well as the motivation for it.
- If it fixes an open issue, please mention that issue number here.
-->

### Important Notes
<!--
- Mention important elements of the design.
- Mention any notable changes to APIs.
-->

### Checklist
Please include the following checklist in your PR:

- [ ] The documentation has been updated if necessary.
- [ ] The code conforms to the [Scala](https://github.com/luna/enso/blob/master/doc/scala-style-guide.md), [Java](https://github.com/luna/enso/blob/master/doc/java-style-guide.md) or [Haskell](https://github.com/luna/enso/blob/master/doc/haskell-style-guide.md) style guides as appropriate.
- [ ] The code has been tested where possible.