Support Multiplayer edit in the designer

[jogibear9988]

Support that more users edit the same document simultanly, like in sigma

see: https://www.figma.com/de/blog/how-figmas-multiplayer-technology-works/

also this may help: https://www.youtube.com/watch?v=oKIThIihv60&t=3441s

we need to check how we support multiple documents