Tests

[biow0lf]

Changes:

1. Improve test coverage:

Coverage report generated for RSpec to /home/runner/work/errbit_github_plugin/errbit_github_plugin/coverage.
Line Coverage: 100.0% (54 / 54)
Branch Coverage: 100.0% (8 / 8)

2. Add rubocop config
3. Rename lib/errbit_github_plugin/error.rb lib/errbit_github_plugin/authentication_error.rb
4. Add faraday-retry gem to gem requirements
5. Add activesupport gem to gem requirements
6. Require ruby version >= 3.1.0
7. Add rake gem to Gemfile
8. Add rspec gem to Gemfile
9. Add simplecov gem to Gemfile
10. Add standard gem to Gemfile
11. Add rubocop gem to Gemfile
12. Add rubocop-disable_syntax gem to Gemfile
13. Add rubocop-performance gem to Gemfile
14. Add rubocop-rake gem to Gemfile
15. Add rubocop-rspec gem to Gemfile