feat: add config "flat/all"

[aladdin-add]

open questions:

1. need to add an equivalent eslintrc config?
   2. need to add language options?

fixes #400

[voxpelli]

I don't think this is a good idea #400 (comment)

[voxpelli]

If we document this the same way as ESLint did in eslint/eslint#19318 then I'm okay with this 👍

[MichaelDeBoey]

If we have clear documentation, I'm fine with merging this as well

[scagood]

Generally 👍 to this documentation is clear and the recommended rules detection is super nice.