[Feature?] Biodome elevator "X days since the last accident" sign

[pali6]

Adds a sign to the infamous biodome elevator that informs you about how many shifts have passed since the last elevator accident (and also the total number of such accidents). Both getting crushed by the elevator and falling down the elevator shaft count! These stats are saved through BYOND savefile, specifically to data/ElevatorStats.sav, yell at me if this is bad or if it's gonna cause problems with how the real server is compiled / deployed.

The only change in the map file is that I added the sign here https://i.imgur.com/SdZvYeQ.png

Here's the sprite of the sign:

compare: https://github.com/goonstation/goonstati...vator-sign