Update dependencies

[AndersGM]

Updated dependencies and removed support for deprecated ruby 2.7.x

[AndersGM]

@r7kamura :-)

[r7kamura]

Thank you!

Dropping support for a specific Ruby version—even if it’s already deprecated—can be a significant change for existing users. For that reason, I plan to address it in a separate pull request. Also, although we haven’t explicitly specified the Ruby version in the gemspec until now, I thought this would be a good opportunity to add it as well.

• Drop Ruby 2.7 support #16

[r7kamura]

The reason we've been running CI on two Ruby versions so far was to ensure coverage for both the minimum supported version and the latest supported version. If we stick with this approach, we should probably include Ruby 3.0 in the CI matrix as well.

In fact, looking at the current Gemfile.lock, I suspect it might not work correctly on Ruby 3.0. I'm not very familiar with the recent state of nokogiri gem. Is it not possible to make a single Gemfile.lock work with both Ruby 3.0 and 3.4? If that's the case, then maybe we should consider maintaining separate Gemfile.lock files for each Ruby version used in CI.
What do you think?