Generate / publish API docs for airshipctl api documents

[seaneagan]

Problem description (if applicable)

It would be useful to have autogenerated api documentation for the airshipctl API documents.

Proposed change

Once we are generating CRDs for all of the airshipctl API types (#574), we can use those to generate / publish api docs,
similar to how we are doing this in sip and vino:
https://github.com/airshipit/sip/blob/master/docs/api/sipcluster.md
https://github.com/airshipit/vino/blob/master/docs/api/vino.md

Once we get the generation in place we could look at publishing airshipctl/sip/vino docs all to https://docs.airshipit.org/

[seaneagan]

https://review.opendev.org/c/airship/airshipctl/+/798167

[sanjib-35]

please assign to me