Analog to digital example

[tsadowski]

Hi, I made an analog example. There is certainly a neater solution than using a counter with the iterator but it is essentially my first rust program.

Cheers, Torsten

[robyoung]

Looks great, thanks @tsadowski. Could you add point to the CHANGELOG about the ADC peripheral being exposed please? Also, it looks like it needs a rustfmt.

[tsadowski]

A language with an official code formatter. Nice!

[bors[bot]]

Build succeeded:

• build (MSRV)
• build (stable)
• Rustfmt