Property functions for modcharts

[bdidk235]

I just find it hard to find stuff I need for modcharts, and I have to make other stuff to do the same thing, requiring extra work, this is just this isn't really a big problem, but it will be nice to fix/improve it.

I made a PR that fixes that stuff!

[bdidk235]

Here's kinda what I mean:

-- Custom Camera Zoom Script (example)
local originalCamZoom = 1
local originalHudZoom = 1
local beatCamZoom = 0
local beatHudZoom = 0

function lerp(a, b, ratio)
	return a + ratio * (b - a)
end

function start()
	originalCamZoom = getCamZoom()
	originalHudZoom = getHudZoom()
end

function update(elapsed)
	beatCamZoom = lerp(0, beatCamZoom, 0.95)
	beatHudZoom = lerp(0, beatHudZoom, 0.95)
	setCamZoom(originalCamZoom + beatCamZoom)
	setHudZoom(originalHudZoom + beatHudZoom)
end

function beatHit(beat)
	if cameraZooms and getCamZoom() < 1.35 and beat % 4 == 0 then
		beatCamZoom = beatCamZoom + 0.015
		beatHudZoom = beatHudZoom + 0.03
	end
end