The `OneOfMany` linter preference type doesn't seem to be documented anywhere

I was planning to add more linters that handle verbs with multiple past participles like "hanged" vs "hung", "dived" vs "dove", "pleaded" vs "pled", and started looking at how I did the "sneaked" vs "snuck" one.

This led me to discover that both "sneaked" and "snuck" are now flagged:

Digging further in #4209 I discovered that this is due to the change in linter configuration from `lint_group/mod.rs` to `default_configuration.json` and the fact that there is a `OneOfMany` type of linter preference that was introduced.

I've looked manually, Googled in both `site:github.com/Automattic/harper` and `site:writewithharper.com`, and asked the built-in coding agent in the Devin fork of VS Code if it can find documentation for `OneOfMany` and we can't find any.

We could still be missing something but it seems to be undocumented and so far not used for any linter.

I have not dug into whether anything needs to be documented downstream for `harper.js` or any of the integrations.

Start by comparing the linter configuration changes in lint_group/mod.rs and default_configuration.json, then trace the OneOfMany preference introduced in the change discussed by #4209. Document what the preference means and how it is configured, and check whether harper.js or other integrations need corresponding documentation.

Written by the indexing model from the issue text.