Add temparature sensor as salt source to compute internal entropy

[vidya88]

@olemis commented on Apr 3

Feature description

Salt internal entropy with values read from ADC temperature sensor .

Additional context
Postponed to finish #141 for v1

This is a type 3 salt source.

Possible implementation

• Quick study of variance to classify salt source.
• Read temperature value
• Mix temperature value with internal entropy

[vidya88]

@olemis commented on May 2

• Quick study of variance to classify salt source.

@stdevIvr this could be handled similar to unconnected GPIO , it seems