Multiple tilemaps per world

[cosmiccoincidence]

Summary

Add feature to tilemaps system so that a world (map) can support multiple tilemaps within.

Goal

A world (map) needs to support multiple tilemaps because the space station will be one and each shuttle will be one. This way the shuttles can be easily split from the station and individually moved/rotated.

Document

Tilemap design: https://ss3d.gitbook.io/design/environment/tilemaps

Tilemap system: https://ss3d.gitbook.io/systems/tilemaps

[stilnat]

linking @henkhooft PR as it's the first implementation of this and will surely be useful https://github.com/RE-SS3D/SS3D/pull/736