Function needs_prefix

pub fn needs_prefix(
    arg: &str,
    data: &Everything,
    scopes: Scopes,
) -> Option<&'static str>

Look up a token that’s an invalid target, and see if it might be missing a prefix. Return the prefix if one was found.

scopes should be a singular Scopes flag.

Example: if the token is “irish” and scopes is Scopes::Culture then return Some("culture") to indicate that the token should have been “culture:irish”.