feat: integration with github issues (and other issue tracking services) #155
Description
In order to ensure referenced issues are formatted correctly and exist, it would be nice to have integration with GitHub issues and other similar services. As for implementation, it would be the most helpful to both have autocomplete in text tokens and there to be a dedicated "issue" token that allows choosing from the issues of the connected repo.
This would go really well with #113 if you could type the list, allowing for an issue list.