Add generic interface for retrieving workflows

[MarkRobbo]

Currently only Github is supported

Ideally Gitlab, generic Git and file uploads options would be available

[mr-c]

GitLab support would be great!

https://gitlab.com/unduthegun/stellaris-emblem-lab/blob/cwl/textures/textures.cwl
https://gitlab.com/unduthegun/stellaris-emblem-lab/raw/cwl/textures/textures.cwl

[MarkRobbo]

This is partially completed with the addition of generic git in version 1.1.0

However, file uploads are still not supported and so this issue can remain open to track that possibility

[mr-c]

How about a URL to a single packed workflow?