Add driver for MCP9808 i2c temperature sensor (#676)

mcp9808: add support for temperature sensor

examples/mcp9808/main.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"fmt"
+	"machine"
+	"time"
+
+	"tinygo.org/x/drivers/mcp9808"
+)
+
+func main() {
+
+	//tinygo monitor
+	time.Sleep(time.Millisecond * 5000)
+
+	//Configure I2C (in this case, I2C0 on RPI Pico), and wire the module accordingly
+	machine.I2C0.Configure(machine.I2CConfig{
+		SCL: machine.GP1,
+		SDA: machine.GP0,
+	})
+
+	//Create sensor
+	sensor := mcp9808.New(machine.I2C0)
+	if !sensor.Connected() {
+		println("MCP9808 not found")
+		return
+	} else {
+		println("MCP9808 found")
+	}
+
+	time.Sleep(time.Millisecond * 1000)
+
+	//Set resolution
+	sensor.SetResolution(mcp9808.Maximum)
+
+	time.Sleep(time.Millisecond * 1000)
+
+	//Read temp.
+	temp, err := sensor.ReadTemperature()
+	if err != nil {
+		println("MCP9808 error reading temperature")
+		println(err.Error())
+		return
+	} else {
+		fmt.Printf("Temperature: %.2f \n", temp)
+	}
+	return
+}