Add Game Director proposal

[tom-leys]

Add a proposal page.

Triggers game events to attain a chaos goal. Goal varies during each round to create variety.
By measuring and varying chaos, the director keeps the challenge each round within a fun band. It reacts to player success
or failure by tailoring future events based on current chaos measured.

The Game Director adds new game modes, initially CombatDynamic and CalmDynamic. They can only be triggered by an admin
running for instance addgamerule CalmDynamic. A later PR could put them into automatic rotation.

Full text in the preview: https://github.com/space-wizards/docs/blob/076d601f5fcbe88e2e8c38e0e3464f3c617e3796/src/en/proposals/game-director.md

[Partmedia]

This is the design doc for what is implemented in space-wizards/space-station-14#16548.

The overall design seems reasonable. Of course, how well this actually would behave in round depends on the specific values assigned to events, and to the metrics implemented. The metrics proposed here seem reasonable to me, and more metrics or improved metrics can be introduced with time.

I intend to merge this.