Add support for Rails Annotations and CodeStatistics

[taketo1113]

This Pull Request adds support for Rails Annotations and CodeStatistics.

Annotations

This Pull Request enables the rails notes command recognize TODO comments inside .slim files.

Expected behavior

Annotations inside .slim files are detected.

/app/views/ports/show.html.slim

/TODO: some comment
div
  | sample

$ rails notes
  * [    3] [TODO] some comment

Actual behavior

Annotations inside .slim files are not detected.

/app/views/ports/show.html.slim

/TODO: some comment
div
  | sample

$ rails notes

Details

Below is an example from Rails that shows how additional extensions can be registered for annotations:

# Registers new Annotations File Extensions
Rails::SourceAnnotationExtractor::Annotation.register_extensions("css", "scss", "sass", "less", "js") { |tag| /\/\/\s*(#{tag}):?\s*(.*)$/ }

• https://github.com/rails/rails/blob/bae568c80735bf3dcebcd693293527dbdd5111cc/railties/lib/rails/source_annotation_extractor.rb#L96-L100

CodeStatistics

This change enables .slim files to be counted by the rails stats command.
Rails 8.2 (main branch) introduced a new method, Rails::CodeStatistics#register_extension, which allows gems to register additional file extensions.
When running on Rails 8.2 or later, this Pull Request registers the slim extension with Rails::CodeStatistics.

• Add Rails::CodeStatistics#register_extension to register file extensions for rails stats rails/rails#56017

For reference, here is an example of how to register an extension:

Rails::CodeStatistics.register_extension("slim")

• https://github.com/rails/rails/blob/bae568c80735bf3dcebcd693293527dbdd5111cc/railties/lib/rails/code_statistics.rb#L66-L72

[taketo1113]

I opened the Issue (#207) because I encountered a situation where the slim-rails version was downgraded during local testing this feature.

[taketo1113]

I have rebased to add CI for Rails 8.1.

[taketo1113]

Thank you for reviewing.