node-red/.github/PULL_REQUEST_TEMPLATE.md

<!--
## Before you hit that Submit button....

Please read our [contribution guidelines](https://github.com/node-red/node-red/blob/master/CONTRIBUTING.md)
before submitting a pull-request.

## Types of changes

What types of changes does your code introduce?
Put an `x` in the boxes that apply
-->

- [ ] Bugfix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)

<!--
If you want to raise a pull-request with a new feature, or a refactoring
of existing code, it **may well get rejected** if it hasn't been discussed on
the [mailing list](https://groups.google.com/forum/#!forum/node-red) or
[slack team](https://nodered.org/slack) first.

-->

## Proposed changes

<!-- Describe the nature of this change. What problem does it address? -->

## Checklist
<!-- Put an `x` in the boxes that apply -->

- [ ] I have read the [contribution guidelines](https://github.com/node-red/node-red/blob/master/CONTRIBUTING.md)
- [ ] For non-bugfix PRs, I have discussed this change on the mailing list/slack team.
- [ ] I have run `grunt` to verify the unit tests pass
- [ ] I have added suitable unit tests to cover the new/changed functionality