Fix: Monster tokens throw Polyglot errors

[NekohimeMusou]

Whenever you select a monster token with the Polyglot mod enabled, it emits at least one console error telling you that it can't find the actor's languages because system.languages.value is undefined. As far as I know it's basically harmless, but depending on what I'm doing it can spit hundreds or thousands of bright red error messages that make debugging a pain.

This quick fix eliminates the spam by placing an empty array where Polyglot expects to find it: first by moving the template.json definition for the languages field from the PC actor type into the common template shared by both, then adding migration code to correct the behavior for old monsters.