refs #17 Add VishayTherm.

Arbitrary name for now. Vishay is the manufacturer of the thermistor I'm
testing this with.

src/drivers/vishaytherm.cpp

@@ -0,0 +1,14 @@
+#include "drivers/vishaytherm.hpp"
+
+#include "unit_config.hpp"
+
+void VishayTherm::init() {
+}
+
+ThermistorReading VishayTherm::readTherm() {
+  ThermistorReading reading;
+
+  reading.celsius = 2.345f;
+
+  return reading;
+}

src/drivers/vishaytherm.hpp

@@ -0,0 +1,19 @@
+#ifndef VISHAYTHERM_HPP_
+#define VISHAYTHERM_HPP_
+
+#include <cstdint>
+
+#include "hal.h"
+
+#include "drivers/adc_device.hpp"
+#include "sensor/thermistor.hpp"
+
+class VishayTherm : protected ADCDevice<2, 4>, public Thermistor {
+public:
+  using ADCDevice::ADCDevice;
+
+  void init() override;
+  ThermistorReading readTherm() override;
+};
+
+#endif