Rename the julia-version input to channel

[DilumAluthge]

Fixes #59

This is a breaking change.

[DilumAluthge]

@davidanthoff I went with channel here, but if you prefer, I can rename it to juliaup-channel.

[davidanthoff]

I think channel makes the most sense. The only time we add julia to that name is for the env var JULIAUP_CHANNEL, but that is only because it is essentially a global namespace. Everywhere else where it is clear that things are in the Juliaup context, we just use channel, so I think that makes most sense here as well. So: thumbs up :)

[DilumAluthge]

I'll hold off on merging this until we decide if there any other breaking changes we want to make. Then we can make a single breaking release that includes all of the breaking changes in a single release.

[DilumAluthge]

@davidanthoff Shall we merge this now, and tag a breaking v2?

Are there any other breaking changes that we want to include in v2?

[davidanthoff]

Looks good to me, I'd say lets merge and do a v2! I can't think of any other breaking things right now.

[DilumAluthge]

I'll create the v2.0.0 and v2 tags.

[DilumAluthge]

My TODO list:

• Create the v2.0.0 tag and corresponding GitHub Release
  • https://github.com/julia-actions/install-juliaup/releases/tag/v2.0.0
• Create the v2 tag (that just points to the v2.0.0 tag
  • https://github.com/julia-actions/install-juliaup/releases/tag/v2
• Update the README to replace all occurrences of v1 with v2
  • Docs: change all instances of v1 to v2 #66

[DilumAluthge]

I have finished the tasks in my above TODO list.