Added get_adc_voltage()

[Malaphor]

Added new enum and prototype to can_simple.hpp Added a new entry in the switch statement and the callback function to can_simple.cpp

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
4 out of 5 committers have signed the CLA.

:white_check_mark: Wetmelon
:white_check_mark: nick-a-schneider
:white_check_mark: Malaphor
:white_check_mark: samuelsadok
:x: dependabot[bot]
_{You have signed the CLA already but the status is still pending? Let us recheck it.}