Add Ruby 3.3 to CI matrix

[m-nakamura145]

This PR adds Ruby 3.3 to CI matrix.

[mikegee]

Thank you for the contribution! ❤️

Looks like we need a bit of maintenance on that Lint check. There's a bunch of warnings too. (I'm a little embarrassed.)

Do you feel like helping on those?

[m-nakamura145]

@mikegee Of course! Should I fix the tests where Rubocop warnings were issued in this Pull Request?

[mikegee]

I'm glad you are willing to help. Separate or together are both fine with me. Those fixes aren't related to this PR, but you could put them together as "maintenance" in one PR, if you want.

[m-nakamura145]

@mikegee Thank you! I will add new commits to this Pull Request. Is it okay to proceed with the approach of fixing the tests that generated warnings, without changing the Rubocop RSpec/ExampleLength rules?"

[mikegee]

🤔 Looks like RSpec/ExampleLength wants our examples 5 or fewer lines. I don't think that's worth rewriting a lot of specs. I think we should set a project setting for that cop to allow 11 or whatever makes it stop complaining. 11 line examples don't seem that bad to me.

But, I'm happy to accept any approach you want.

[m-nakamura145]

@mikegee I agree with your opinion. I have added the RSpec/ExampleLength setting to .rubocop.yml.
ca8ffb7

[mikegee]

Thanks so much!