Description

#3282 suggests introducing a way to get structured data about which rules were migrated and which were not.

We could expose a new CLI option --reporter to emit a report that output this kind of information.
We could support a JSON output. I am not sure if we need another reporter. However, using a --reporter option makes the interface consistent with other commands that also use the reporter concept.

❯ biome migrate eslint --reporter=json
{
    // format to define
}