feat: Annotation support for table comment

[TomohikoSato]

Add annotation support for table comment.

It would be useful for many people because table comment is recommended as described in the rails guide.

https://guides.rubyonrails.org/active_record_migrations.html

It's highly recommended to specify comments in migrations for applications with large databases as it helps people to understand data model and generate documentation.

[ctran]

Thanks. Could you post an example with both table and column comments?

[TomohikoSato]

@ctran

Could you post an example with both table and column comments?

OK. added 8195810

I resolved the CI error by cherry-picking 5cc83c6, same as https://github.com/ctran/annotate_models/pull/793#issuecomment-814690403