Sub-issues support

[leog]

Creating Linear sub-issues in a parent issue should be mapped to a parent GH issue with children sub-issues linked by a task list

[tedspare]

Hey @leog, great idea! I don't personally have the bandwidth to add this (would require some work ensuring task list doesn't show up in Linear) - would you want to give it a try? Otherwise I might close it as stale

[leog]

@tedspare sure, I can take it as a side project 👍