Add support more Capybara debugger entry points for Lint/Debugger

[ydah]

This PR makes add support more Capybara debugger entry points for Lint/Debugger

• page.save_and_open_page
• page.save_and_open_screenshot
• page.save_page
• page.save_screenshot
• save_page
  • https://www.rubydoc.info/gems/capybara/Capybara%2FSession:save_page
• save_screenshot
  • https://www.rubydoc.info/gems/capybara/Capybara%2FSession:save_screenshot

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Before submitting the PR make sure the following are checked:

• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Ran bundle exec rake default. It executes all tests and runs RuboCop on its own code.
• Added an entry (file) to the changelog folder named {change_type}_{change_description}.md if the new code introduces user-observable changes. See changelog entry format for details.

[ydah]

One thing that bothers me is that I think one of the future improvements would be to create a cop in rubocop-capybara to detect the debugger entry point for capybara and remove the entry point for capybara from rubocop. I don't have a particularly strong opinion, but the benefit of extracting to rubocop-capybara is that Lint/Debugger doesn't allow you to specify the path to exclude for each entry point type, and this cop check is enabled by default even if you're not using Capybara. However, since method names are quite distinctive, the same method name might not be defined and there might not be many false positives. WDYT?

[koic]

One thing that bothers me is that I think one of the future improvements would be to create a cop in rubocop-capybara to detect the debugger entry point for capybara and remove the entry point for capybara from rubocop

I generally agree. However, instead of creating a new Cop for RuboCop Capybara, it might be smarter to move the Lint/Debugger configuration specifically for Capybara to RuboCop Capybara. The following RuboCop Rails's PR may serve as a reference:
rubocop/rubocop-rails#1097

[bbatsov]

As there's already some Capybara config in RuboCop I think it's fine to merge the configuration changes. We can discuss separately injection of configuration from plugins, as that's a broader topic.

[koic]

Thanks!