Update Vision Statement

[AlecWhite]

Is your feature request related to a problem? Please describe.

Now that BN has got some traction I think it would help to update the game's Vision Statement and maybe work in a Game Design Document and this is taking into account the monolithic task of fixing the game engine that is still pending.

I think it would help a lot to clarify how "roguelike"/"roguelite and "sandbox" the game is meant to be. And to differentiate it more from DDA besides the vague "it has less realism and has more sci-fi stuff".

Describe the solution you'd like

Make an updated Vision Statement for the future of Bright Nights.

Additional context

I make this after the Nth time we had a discussion on Discord about what is the intended path that BN is taking.