Implement game physics

[Rekkonnect]

The game's physics (including player velocity and hitboxes) should be registered to allow playtesting levels in the editor.

[naoei]

Reviving on this issue a bit, there's been a recent physics decompilation project authored by Camila314 which is finished.

This will ultimately be a great helping hand as its the closest we're ever going to get in terms of recreating the physics.