lis2mdl: add LIS2MDL magnetometer (#187)

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

examples/lis2mdl/main.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"machine"
+	"time"
+
+	"tinygo.org/x/drivers/lis2mdl"
+)
+
+func main() {
+	machine.I2C0.Configure(machine.I2CConfig{})
+	compass := lis2mdl.New(machine.I2C0)
+
+	if !compass.Connected() {
+		for {
+			println("LIS2MDL not connected!")
+			time.Sleep(1 * time.Second)
+		}
+	}
+
+	compass.Configure(lis2mdl.Configuration{}) //default settings
+
+	for {
+		heading := compass.ReadCompass()
+		println("Heading:", heading)
+
+		time.Sleep(time.Millisecond * 100)
+	}
+}