Update electronics documentation

[dyamon]

We took some time to experiment with the AccelStepper library for Arduino and the RAMPS 1.4 Smart Controller and we should document them.

Here is a non-exhaustive list of things to document:

• [ ] Overview of the examples
• [ ] How to use the rotary encoder in the Smart Controller (via the [Encoder library])(https://www.arduino.cc/reference/en/libraries/encoder/);
• [ ] How to use the AccelStepper library (right instantiation method and caveats with inverted pins);
• [ ] How to use the LCD display and its limitation while driving stepper motors.
• [ ] How to drive two motors (in opposite directions) with the same signal.
• [ ] More details on microstepping for drivers