add stamps and envelopes to disposal bins

[Deathrobotpunch1]

envelopes should be able to hold a maximum of two small items and stamps are used to mark a destination for said envelope. also a disposal bin that only allows mail to be sent through it would be cool for prisoners too.

it kinda sucks that mail is underused as a whole and this would be neat both as a crewmember and a traitor (did you know there is a tot item that allows you to trap letters or put large items in them)