Add USB HID joystick support (#3366)

machine/usb: add USB HID joystick support

src/examples/hid-joystick/main.go

@@ -0,0 +1,27 @@
+package main
+
+import (
+	"log"
+	"machine/usb/joystick"
+	"math"
+	"time"
+)
+
+var js = joystick.Port()
+
+func main() {
+	log.SetFlags(log.Lmicroseconds)
+	ticker := time.NewTicker(10 * time.Millisecond)
+	cnt := 0
+	const f = 3.0
+	for range ticker.C {
+		t := float64(cnt) * 0.01
+		x := 32767 * math.Sin(2*math.Pi*f*t)
+		button := cnt%100 > 50
+		js.SetButton(2, button)
+		js.SetButton(3, !button)
+		js.SetAxis(0, int(x))
+		js.SendState()
+		cnt++
+	}
+}