add --path to biome migrate eslint|prettier to specify config file

[DerTimonius]

Description

I am currently in the process of migrating a monorepo from eslint to Biome and since our eslint config lives in a shared internal package, biome migrate eslint does not correctly detect it.

Adding the --path option for the migrate command could help where the user has to specify where the config file is located.

pnpm biome migrate eslint --write --path packages/eslint/config.js

A similar option should also be possible for prettier.

Open questions

• Should the user define if the eslint config is flat or legacy? It's probably not always obvious based on the name of the config file
• If they have to define the config type, what's the best approach?

I would be open to give the implementation a shot, but it might take some time 😅