Add release drafter workflow.

[jenskeiner]

This PR adds a new workflow that runs on every merge to develop. It then creates or updates a draft GitHub release for the next patch version with a changelog based on PRs merged.

I have used this action in other projects and it was a good way to keep a list of changes since the last release. However, one must typically review and adjust the change log before a release since PR titles and descriptions are not always best suited for a changelog.

[codspeed-hq]

CodSpeed Performance Report

Merging #174 will not alter performance

_{Comparing feature/release-drafter (dea666b) with develop (8bec298)}

Summary

✅ 88 untouched
🗄️ 154 archived benchmarks run¹

Footnotes

1. 154 benchmarks were run, but are now archived. If they were deleted in another branch, consider rebasing to remove them from the report. Instead if they were added back, click here to restore them. ↩