New Eastern European OSShD Signals

[DasCapschen]

We should add some more signals to provide people with a wider range of countries to create maps in.
The OSShD signals seem similar to the east-german HL signals, so will probably be easy to add.
I think they might require new models, and slightly different light setups, but the logic should largely remain the same :)

Feature requested by Hazzza on Discord.

Edit: Link to these signals https://sh1.org/osshd/s.htm