PULL_REQUEST_TEMPLATE

## :camera: Screenshots
<!-- Show us what you've changed, we love images. -->

## :page_facing_up: Context
<!-- Why did you change something? Is there an [issue](https://github.com/ChuckerTeam/chucker/issues) to link here? Or an external link? -->

## :pencil: Changes
<!-- Which code did you change? How? -->
<!-- If your changes affect users somehow, be it a new feature, a bugfix or an API change please update the `Unreleased` section in the CHANGELOG.md file. -->

## :paperclip: Related PR
<!-- PR that blocks this one, or the ones blocked by this PR -->

## :no_entry_sign: Breaking
<!-- Is there something breaking the API? Any class or method signature changed? -->

## :hammer_and_wrench: How to test
<!-- Is there a special case to test your changes? -->

## :stopwatch: Next steps
<!-- Do we have to plan something else after the merge? -->