Feature request: Add IO.VIN enum member to read the voltage

[BenediktBurger]

It would be good to read the voltage of the motor cards.

I found, that it is possible to read that voltage via get_analog_input, if you know the correct pin number.

I see two possible options:

1. add a get_voltage method (which does the correct calculation to return the voltage in Volts)
2. add a VIN enum member to the IO enum of the motor cards, see my PR Add VIN to IO enum of TMCM6110 #103 for one motor card.

Thanks for considering.

[trinamic-bp]

It could actually be both, I accepted you PR, but the get_voltage would come in handy as well.
Note that the added VIN is not in the released PyTrinamic on PyPI, till we create a new release.

[BenediktBurger]

I understand, that it will take some time till the next release.
However, I did not do it for immediate change ("8" will work as well), but for a better library.