new workflows with: setting arbitrary env vars, determine available perl versions dynamically

[tomk3003]

I added new workflows, since I introduced braking changes.
Having done that I changed testing_context to environment as well.
Should you want to accept the PR, I could update the README.md as well.

Environment vars can be set with:

    with:
      os: '["ubuntu-latest"]'
      environment: |
        {
          "MY_TEST_VAR": "MY_TEST_VALUE",
          "SECOND_VAR": "SECOND_VALUE"
        }

[davorg]

This looks great, thanks.

If you update the README and add details of the breaking changes, then I really don't mind if your versions overwrite the originals.

[tomk3003]

I could do that.
But wouldn't it be generally a good idea to change to a versioned approach with breaking changes resulting in a version upgrade with a release tag?
And move the workflows out of the .github/workflows directory?
I would really like to use them as:

jobs:
  test:
    uses: PerlToolsTeam/github_workflows/cpan-test@v2

If I read the docs correctly, this would also allow users to let dependabot handle updates.
I would be happy to help with that.

[davorg]

Yes. Sorry, that's exactly what we should do. Let me have a look at what other, similar, repos do.