Custom reporter support

[mongolyy]

Overview

I would like Biome to support user-defined custom reporters.

Background / Motivation

• I use reviewdog. Reviewdog requires diagnostic messages to be formatted in its own RDFormat. Currently, Biome does not provide a way to extend or override the output format easily.
• ESLint offers the ability to specify a custom format via its -f / --format option. Users who have leveraged custom formatters in ESLint would also benefit from a similar feature in Biome.

[ematipico]

Biome already has different different reporters: https://biomejs.dev/reference/reporters/

--reporter=<json|json-pretty|github|junit|summary|gitlab>