add allowStaticMovers field to SeekerBarrier

[microlith57]

basic loenn plugin for testing:

local seekerBarrier = {}

seekerBarrier.name = "seekerBarrier"
seekerBarrier.depth = 0
seekerBarrier.color = {0.25, 0.25, 0.25, 0.8}
seekerBarrier.placements = {
    name = "seeker_barrier",
    alternativeName = "jellyfish_barrier",
    data = {
        width = 8,
        height = 8,
        allowStaticMovers = true -- If disabled, static movers like spikes won't attach to the barrier.
    }
}


return seekerBarrier