[Airsoft] ADAR-15 split stock

Remixed the stock to be split in 2 so it fits on a stock (haha get it?) Creality Ender 3. Other edits include a separate selector detent spring holder based off the Hera CQB stock so it doesn't mangle the spring when you take it down (I recommend using a razor blade for popping it out), added clearance for a castle nut and end plate, and included the buttplate made by Bearsoft in this remix (https://www.thingiverse.com/thing:4809020).

The models are in spec, but you probably will have to do a bit of filing down the nubs on the Bottom so it fits snugly in the Top.