WIP Update Rubocop

[iurev]

Important updates:

• dropped support for ruby 2.3 because anycable gem supports ruby >= 2.7 (which is also non-secure already)
• moved dev gems from gemspec to Gemfile
• added rubocop workflow to GitHub Actions
• manually fixed some rubocop warnings

Future plans:

• [x] finish rubocop_todo.yml. It will require me to refactor some tests and dive deeper into the project, which is a good thing.

[Envek]

dropped support for ruby 2.3 because anycable gem supports ruby >= 2.7 (which is also non-secure already)

I'm fine with that, but then we probably need to bump anycable version in gemspec to one that started to require Ruby 2.7.

In general it is better to support older Rubies as long as possible, maybe with help from ruby-next (there are a lot applications on old unmaintained Rubies in the wild)

moved dev gems from gemspec to Gemfile

:+1:

[iurev]

I'm fine with that, but then we probably need to bump anycable version in gemspec to one that started to require Ruby 2.7.

In general it is better to support older Rubies as long as possible, maybe with help from ruby-next (there are a lot applications on old unmaintained Rubies in the wild)

@Envek, AnyCable supports ruby >= 2.7. I think in this case supporting the same ruby version is enough. Link to AnyCable Requirements