xk x100 bigger battery mount / stand

Needed to use other batteries, including the v977 / k110 ones and some even bigger ones.

This has two different spaces, one for slim batteries and one for larger (8-9mm height).
It also serves as steady feet for the drone, limiting impact on the motors when landing.
It replaces the aileron side but requires the top part battery holder to be in place (it clips into it).

I printed it in ABS at 0.2mm height with a 0.4mm nozzle, it's just enough flex and strength.