l293x: added support for h-bridge motor controller

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

examples/l293x/simple/main.go

@@ -0,0 +1,34 @@
+package main
+
+import (
+	"machine"
+	"time"
+
+	"tinygo.org/x/drivers/l293x"
+)
+
+func main() {
+	wheel := l293x.New(machine.D10, machine.D11, machine.D12)
+	wheel.Configure()
+
+	for i := 0; i <= 10; i++ {
+		println("Forward")
+		wheel.Forward()
+		time.Sleep(time.Millisecond * 1000)
+
+		println("Stop")
+		wheel.Stop()
+		time.Sleep(time.Millisecond * 1000)
+
+		println("Backward")
+		wheel.Backward()
+		time.Sleep(time.Millisecond * 1000)
+
+		println("Stop")
+		wheel.Stop()
+		time.Sleep(time.Millisecond * 1000)
+	}
+
+	println("Stop")
+	wheel.Stop()
+}