Holding this feather makes you light as it
- A item when held in the players hand will allow any negative velocity to become reduced to a slow enough speed that no fall damage will be taken
- Optional crafting of the feather
Just add feather_fall.craftable = true to your minetest.conf (and restart if needed).
First run will create this setting to false, so you could just run it first then edit your
minetest.conf.