Book bags for the librarian

In a bid to encourage more Librarians to actually do their jobs, I present: Plant Bag, mashed wood edition.

Features:
- Can hold normal books and spellbooks!
- One-click unloading at bookcases!
- Spawns on your hand at roundstart!
- Available at a Biogenerator near you for the low low cost of 200 biomass!

The barcode scanner, which previously spawned on the left hand, was displaced to the right pocket.
Also, I can't sprite for shit, so the current sprite is a poorly made red recoloring of the mining satchel.
This is also my first time submitting a PR here, so be please gentle~