add compression middleware to worldmap

package.json

@@ -4,6 +4,7 @@
     "description": "A Node-RED node to provide a web page of a world map for plotting things on.",
     "dependencies": {
         "cgi": "0.3.1",
+        "compression": "^1.7.4",
         "express": "^4.16.4",
         "sockjs": "^0.3.19"
     },

worldmap.js

@@ -18,6 +18,7 @@ module.exports = function(RED) {
     "use strict";
     var path = require("path");
     var express = require("express");
+    var compression = require("compression");
     var sockjs = require('sockjs');
     var sockets = {};
     RED.log.info("Worldmap version " + require('./package.json').version );
@@ -53,6 +54,7 @@ module.exports = function(RED) {
         this.log("started at "+this.path);
         var node = this;
         var clients = {};
+        RED.httpNode.use(compression());
         RED.httpNode.use(node.path, express.static(__dirname + '/worldmap'));
 
         var callback = function(client) {