examples: add example for mag3110 magnetometer

Signed-off-by: Ron Evans <ron@hybridgroup.com>

examples/mag3110/main.go

@@ -0,0 +1,22 @@
+// Connects to an MAG3110 I2C magnetometer.
+package main
+
+import (
+	"machine"
+	"time"
+
+	"github.com/tinygo-org/drivers/mag3110"
+)
+
+func main() {
+	machine.I2C0.Configure(machine.I2CConfig{})
+
+	mag := mag3110.New(machine.I2C0)
+	mag.Configure()
+
+	for {
+		x, y, z := mag.ReadMagnetic()
+		println(x, y, z)
+		time.Sleep(time.Millisecond * 100)
+	}
+}