Help adding E-Ink display support

So i haven't fully tested this, but this is the intended way i was going to get around the idea of somebody trying to draw something when the pin is busy.

This will only stop one draw that was added too quickly. Since its still using the same image buffer. But its primarily there just so it doesn't crash the board.

SSD16xx.prototype.flip = function() {
    if(this.unInit == true){
      return this.init().then(()=>{
        return this.flip();
      });
    }
   if(this.busyPin.read()){
      return new Promise((resolve)=>{
          setWatch(resolve, this.busyPin, { repeat:false, edge:'falling' });
      }).then(()=>{
         return this.flip();
      });
   }

    this.scd(0x4E, 0);
    this.scd(0x4F, [0,0]);
    if(this.partialTran == true){
      this.partialTran = false;
      this.scd(0x26, this.g.bw.buffer);
      this.scd(0x24, this.g.bw.buffer);
    }
    else{
      this.scd(0x24, this.g.bw.buffer);
    }


    if(this.display.coloredDisplay){
        this.scd(0x4E, 0);
        this.scd(0x4F, [0,0]);
        this.scd(0x26, this.g.cw.buffer);
    }

    return this.refreshDisplay();
};