Add 'logger' as dependency in gemspec

[leoarnold]

Follow up to #399.

[johnnagro]

Thanks for the follow-up @leoarnold - consolidating logger into the gemspec (and dropping the Gemfile duplicate) makes sense.

One thing though: unlike base64/bigdecimal/mutex_m (which we only need so older Rails can load in our test matrix), logger is required by lograge's own runtime code (require 'logger' in lib/lograge.rb). Since we support activesupport >= 4, and activesupport didn't declare logger as a runtime dependency until Rails 7.1, an app on Rails ≤ 7.0 with Ruby 3.5+ (where logger is no longer a default gem) could fail to load lograge but, a development_dependency wouldn't help those users.

What do you think about making it s.add_dependency 'logger' (runtime) instead? That protects consumers, and it can stay out of the dev block / Gemfile entirely. Happy to merge once that's adjusted.

[johnnagro]

@leoarnold lemme figure out how we might relax/ignore that rubocop rule breaking your build.