Ability to use media keys with Pico over USB HID

Hi! While we don't have a library for this via USB, there is one for Bluetooth HID (http://www.espruino.com/BLE+Keyboard). I haven't tried this out, but just mashing the two bits of code together may work:

E.setUSBHID({
  reportDescriptor : [
  0x05, 0x0c,                    // USAGE_PAGE (Consumer Devices)
  0x09, 0x01,                    // USAGE (Consumer Control)
  0xa1, 0x01,                    // COLLECTION (Application)
                                 // -------------------- common global items
  0x15, 0x00,                    //   LOGICAL_MINIMUM (0)
  0x25, 0x01,                    //   LOGICAL_MAXIMUM (1)
  0x75, 0x01,                    //   REPORT_SIZE (1)    - each field occupies 1 bit
                                 // -------------------- misc bits
  0x95, 0x05,                    //   REPORT_COUNT (5)
  0x09, 0xb5,                    //   USAGE (Scan Next Track)
  0x09, 0xb6,                    //   USAGE (Scan Previous Track)
  0x09, 0xb7,                    //   USAGE (Stop)
  0x09, 0xcd,                    //   USAGE (Play/Pause)
  0x09, 0xe2,                    //   USAGE (Mute)
  0x81, 0x06,                    //   INPUT (Data,Var,Rel)  - relative inputs
                                 // -------------------- volume up/down bits
  0x95, 0x02,                    //   REPORT_COUNT (2)
  0x09, 0xe9,                    //   USAGE (Volume Up)
  0x09, 0xea,                    //   USAGE (Volume Down)
  0x81, 0x02,                    //   INPUT (Data,Var,Abs)  - absolute inputs
                                 // -------------------- padding bit
  0x95, 0x01,                    //   REPORT_COUNT (1)
  0x81, 0x01,                    //   INPUT (Cnst,Ary,Abs)
  0xc0                           // END_COLLECTION
  ]
});

function p(c,cb) { E.sendUSBHID([c]);cb(); }
next = function(cb) { p(0x1,cb) };
prev = function(cb) { p(0x2,cb) };
stop = function(cb) { p(0x4,cb) };
playpause = function(cb) { p(0x8,cb) };
mute = function(cb) { p(0x10,cb) };
volumeUp = function(cb) { p(0x20,cb) };
volumeDown = function(cb) { p(0x40,cb) };