Preliminary thermistor abstraction implementation

[samderanova]

Resolves #37 through the following:

• Create new LimTemperature abstraction in components/
• Add simple demo in demo.rs that reads from the ADS1015

To test the component individually, comment out the code in demo.rs that creates an instance of PressureTransducer, as not doing so will cause an I2C error. Build and run the pod operation executable on a Raspberry Pi 4B and observe the values being printed in millivolts.

Note: A slight issue is that when the voltage drop across the thermistor approaches smaller values, the readings are off by a certain number of millivolts.

[taesungh]

Nice start on reading a single value. We can take the issue in two steps if you feel adding multiple input pins (and multiple ADCs?) would be a big step, but would like to at least see the conversion equation.

[samderanova]

As mentioned in this comment, there are currently some issues with the thermistor's resistances not following what is shown on the datasheet. However, the code to read the values from the ADS1015 works, since we tested in lab with the multimeter.

For now, I'll unlink #37 so that the issue doesn't get closed as completed when this PR is merged but I'll mark the first bullet point as completed when this PR gets merged.

[taesungh]

Works out for now. As discussed, next step is adding the actual temperature conversion.