mDNS is working with Bonjour

I tweaked Gordon's example code snippet for flexibility:

wifi.enableMDNS = function(hostname, serviceType, port, callback) {
	let mdns = "AT+MDNS=1," + JSON.stringify(hostname) + "," + JSON.stringify(serviceType) + "," + JSON.stringify(port) + "\r\n";
	this.at.cmd(mdns, 500, function(d) {
		callback(d);
	});
};

Now you can specify the service type and port, like this:

wifi.enableMDNS("esp-livingroom", "iot", 80, function(result) {
    console.log("result is " + result);
});