Improve Github Action for testing various combinations of ruby/faraday/active[support|model]

[LeipeLeon]

I took the liberty to update the Github action to improve the tests.

Also made these decisions:

• Setup appraisals for all major.minor versions of active[support|model] >= 6
• Test w/ faraday 1.x & 2.x on various ruby's and latest active[support|model]
  • ruby: 3.0, 3.1, 3.2, 3.3, 3.4
• When all ruby test passes run all combinations of ruby/faraday/active[support|model]
  • ruby: 3.0, 3.1, 3.2, 3.3, 3.4
  • faraday: 1.x, 2.x
  • activesupport/activemodel: 6.0, 6.1, 7.0, 7.1 ,7.2, 8.0
  • Exclude unsupported versions:
    • activesupport ~> 7.2.0 depends on Ruby >= 3.1.0
    • activesupport ~> 8.0.0 depends on Ruby >= 3.2.0
• Added mutex_m and base64 to the development dependencies to make tests pass.
• Updated the README with basic instructions for local development.

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