* Events.OnCollide now receives a CollideEvent object, which makes
available the .Actor who collided and the .Overlap rect which is
zero-relative to the target actor. Doodad scripts can use the .Overlap
to see WHERE in their own box the other actor has intruded.
* Update the LockedDoor and ElectricDoor doodads to detect when the
player has entered their inner rect (since their doors are narrower
than their doodad size)
* Update the Button doodads to only press in when the player actually
touches them (because their sizes are shorter than their doodad
height)
* Update the Trapdoor to only trigger its animation when the board
along its top has been touched, not when the empty space below was
touched from the bottom.
* Events.OnLeave now implemented and fires when an actor who was
previously intersecting your doodad has left.
* The engine detects when an event JS callback returns false.
Eventually, the OnCollide can return false to signify the collision is
not accepted and the actor should be bumped away as if they hit solid
geometry.
* Add sync.WaitGroup to some parts of the level collision detection
function and Canvas.Loop() to speed up the frame rate by load
balancing some work in parallel across multiple cores.
* Improves FPS from 30 to 55+ even for busy scenes with lots of mobile
enemies walking around.
* Before the level collision optimization, framerate would sometimes dip
to 30 FPS simply to move the player character on a completely blank
map!
* Move all collision code into the pkg/collision package.
* pkg/doodads/collision.go -> pkg/collision/collide_level.go
* pkg/doodads/collide_actors.go for new Actor collide support
* Add initial collision detection code between actors in Play Mode.
Noah