Suggestion feature

[ohbarye]

Issue

closes #28

Changes

This pull request adds a feature to make the reviewdog create a comment with a suggestion. Like below:

Here's an example pull request to utilize the feature: ohbarye/rubocop-suggestion-example#4

Design

First, I added RdjsonFormatter class in Ruby so that rubocop gets able to generate rdformat JSON. I followed some instructions to implement a new formatter, e.g. https://docs.rubocop.org/rubocop/formatters.html, https://www.rubydoc.info/gems/rubocop/RuboCop/Formatter/BaseFormatter.

Second, I added a test for RdjsonFormatter. I just followed the way of https://github.com/reviewdog/action-eslint. Add test data, shell script, and CI setting.

[gagalago]

awesome. can be interesting to upstream the RdjsonFormatter at some point to gain fix and feedback from a bigger community but I suppose that for now it better to keep it in this repository to have it faster released with reviewdog.

[ohbarye]

@mgrachev @adnikiforov I'd be glad if you'd review this when you have time. 🙏

[mgrachev]

@ohbarye I'm sorry for the long answer. I was on vacation.

Thank you for your contribution! Please resolve a conflict 🙏

[mgrachev]

Also, please fix all rubocop warnings and disable them
https://github.com/reviewdog/action-rubocop/pull/48/files#diff-09318eb08af7c21da437d23a5f268ad408b01f1f7a4a76fecaa2219f6a1bf73bR1

[ohbarye]

@mgrachev
Sorry for leaving this PR failing on CI. 🙏
I've fixed conflicts and failures on CI, then reorganized files and directories in order to follow the preceding change.

[mgrachev]

@ohbarye Thanks a lot for your help 💚

[ohbarye]

@mgrachev Thank you for your review too! 👏