Please add documentation for, and add `withDirConfig()` to the `QueryBuilder` TS interface

[MatthewAry]

Is your feature request related to a problem? Please describe

See https://github.com/nuxt/content/issues/2195

I was going crazy as to why I couldn't find a feature that should allow me to get properties from the _dir.yml file in same folder for the document I was querying, and then I found that it exists, but it was:

1. Not documented
2. Not included in queryBuilder interface

Basically it would be unreasonable to expect someone to find this functionality.

withDirConfig() is undocumented and untyped.

Describe the solution you'd like

Please add a type for withDirConfig() in https://github.com/nuxt/content/blob/f65657f051206f5dd79b0ccc4825c8def7accff1/src/types/content.ts#L436-L499