Replace defunct Travis CI integration with GitHub Actions

[jviotti]

The GitHub Actions setup is equivalent to the Travis CI configuration with two differences:

• The GitHub Action setup does not set the TAG environment variable, as it didn't seem like xml2rfc would consume that at all (unless I'm missing something)

• The GitHub Action preserves the spec output (txt and html) as artifacts that can be downloaded after a successful run (to see the changes without having to locally render the specs)

Fixes: https://github.com/json-schema-org/json-schema-spec/issues/1262 Signed-off-by: Juan Cruz Viotti [email protected]

[jviotti]

@Relequestual I think you might need to enable the repository to run GitHub Actions from forks to be able to test this out. Once it is merged, we should also make this check required.

[gregsdennis]

What I've had to do in json-everything is merge fork PRs into a secondary branch, just to get all of the actions to run properly (even when you get them running, they don't always have all the permissions they need). Then I have another PR to pull into the primary branch.

[Relequestual]

I believe this will also upload requirements.txt to the artifact bundle.

[jviotti]

Good catch @Relequestual ! Fixed.

[Relequestual]

I decided to merge this immediatly as our current CI simply doesn't work.