Create Backpack, chest rig for ZeroContact

template:

{
  "type": "loadout",    //Loadout type for adding backpack and chest rig.
  "id": "backpack_t20_umbra",
  "container_size": 25,  //The capacity of the container
  "equipment_slot": "BACKPACK", //Available slots [BACKPACK,RIGS]
  "texture": "textures/models/backpack/backpack_t20_umbra.png",
  "model": "geo/backpack/backpack_t20_umbra.geo.json"
}