Integrate erb-formatter as a Prettier plugin

[ghost]

It would be great if erb-formatter were a Prettier plugin @prettier/plugin-erb. This would free you from having to maintain the Ruby ERB::Formatter VS Code plugin and free users from installing extra tools.

@prettier/plugin-ruby is also Syntax Tree based and could be used as a template for how to do the integration.

Also see the Developing Plugins section of the Prettier docs.

Thank you for this amazing tool!