feat: support slack cli commands with composite action inputs

[zimeg]

Summary

This PR adds support for running Slack CLI commands with this composite action:

- uses: slackapi/slack-github-action/cli@v2
  with:
    command: "version"

Follows earlier efforts and explorations of @ewanek1 in #484 #486 #488 #489 👾 ✨

Notes

• The "nested" structure is recommendation of @WilliamBergamin and I find it makes inputs and outputs of this step much more clear for documentation sake! An earlier approach in ae50e2e demonstrates the "combined" setup.

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.92%. Comparing base (bb7fade) to head (47ed37c).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #560   +/-   ##
=======================================
  Coverage   95.92%   95.92%           
=======================================
  Files          14       14           
  Lines        2697     2697           
=======================================
  Hits         2587     2587           
  Misses        110      110           

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[zimeg]

A few CLI fixes were needed for windows support in CI. The checks above are using these changes in tests:

🐞 slackapi/slack-cli#178
🌚 slackapi/slack-cli#353