WalkerBotBit stiff version

This is a small modification of the original thing.

In my makes of the original version the parts resulted too flexible, affecting the robot walk.

So I incremented the thickness, and this resulted in better walking.

I also made other mods to support not only servo:lite servoboard, but also ring:bit board.

The .hex file is a sample code to start .

Original project page:
https://www.maffucci.it/2018/01/04/walkerbotbit-two-servo-walking-robot-controlled-by-bbc-microbit-available-3d