Move discussion topic to issue tab or associate with project pipeline

[joshbruce]

https://github.com/markedjs/marked

My team and I were just discussing something:

1. Currently we use Issues to track code problems (issues) and proposals (code changes) because Issues can be directly tied to the project management pipeline (projects, milestones, and so on).
2. Currently there is a way to perform Issue curation by moving certain Issues to Discussions but there doesn't appear to be a way to go the other direction - only move discussions to different repositories...no "Convert to Issue" capability.
3. So, we are currently using Issues for things that will change the code - and discussions for everything else (DevOps, Community, and so on).

My hope as a maintainer would be to keep broken code notices separate from non-broken-code topics.

Whether this allows direct support of Discussion topics in the project management pipeline would be secondary from the ability to convert a Discussion to an Issue (like we can with Issues into Discussions).

ps. Or like we can with project notes in boards...new topic to Issue.

[joshbruce]

See also: #2861