QOL: Add signs & markers so that it is easier to remember and understand the…

QOL: Add signs & markers so that it is easier to remember and understand the factory (+aesthetics).

- If we design some complex part of the factory and return to it later, it might be hard to understand, what is going on there. The direct parallel is comments in the code, they make it easier to understand (even the most readable code requires comments, if it is very complex).
- Signs and markers would be very neat aesthetically, especially with good design. It would be nice to have a wide range of sizes.
An inspiration can be for example airport or spaceport gateway ids.

Another reason if we have a complex crammed blueprint, it would be easy to see which endpoints should be used. For example in this blueprint if we strip the oxygen producer and use the distribution block as a fundamental building block it would be more convenient to understand, which endpoints should be used:
https://hub.coigame.com/Blueprint/Detail/538

Signs are already part of the experimental branch

IN-game with custom Signs