add more useful fields to InvisibleBarrier

[microlith57]

seems useful

note the actual default soundindex is Grass = 33 (apparently for bird nest reasons). a more sensible editor default would be 0 which is silent.

basic loenn plugin for testing:

local invisibleBarrier = {}

invisibleBarrier.name = "invisibleBarrier"
invisibleBarrier.fillColor = {0.4, 0.4, 0.4, 0.8}
invisibleBarrier.borderColor = {0.0, 0.0, 0.0, 0.0}
invisibleBarrier.placements = {
    name = "invisible_barrier",
    data = {
        width = 8,
        height = 8,
        allowClimbing = false, -- If disabled, blocks all climbing when the player is horizontally next to the barrier.
        surfaceIndex = 0, -- Footstep sound when walking on the barrier (or climbing, if enabled).
		allowStaticMovers = true -- If disabled, static movers like spikes won't attach to the barrier.
    }
}

return invisibleBarrier