chore: added `has_type` accessor

[admin-aftermath]

Added the function has_type to accessories.move. This function allows third-party packages to query if a SuiFren contains a given Accessory type.

public fun has_type<T> (sf: &SuiFren<T>, type: String): bool {
    let uid = suifrens::uid(sf);
    dof::exists_(uid, AccessoryKey { type })
}

Without this function, third-party packages will have to blindly add Accessories to a SuiFren which can result in an abort if the SuiFren already has an Accessory of the given type.

This would also enable being able to replace apparel items onchain by querying if an Accessory Type exists first and removing it before adding the new Accessory.