Document compatibility with isort

[Avasam]

Could documentation about compatibility with isort be added?
Specifically, multi_line_output must be set to either 2, 7 or 9
(2-hanging, 7-noqa, 9-vertical-prefix-from-module-import)

OR set include_trailing_comma=true and multi_line_output to 2, 3, 5, 7 or 9
(2-hanging, 3-vert-hanging, 5-vert-grid-grouped, 7-noqa, 9-vertical-prefix-from-module-import)

(note: technically multi_line_output=2 + include_trailing_comma=true is broken, but that's an isort issue that can be fixed eventually (see: PyCQA/isort#1864), I've also omitted 6 as it is deprecated)

Any other mode will result in missing trailing comma or indentation that conflicts with this tool.

[asottile]

I don't think repeating isort's docs here is productive or useful