Add server.js

+const express = require('express');
+const app = express();
+app.use(express.static(__dirname));
+
+app.listen(8080, function(){
+    console.log('listening on 8080');
+});
+
+app.get('/', function(req, res){
+    res.sendFile(__dirname + '/main.html');    
+});
+
+app.get('/main.html', function(req, res){
+    res.sendFile(__dirname + '/main.html');
+});
+
+app.get('/introduction.html', function(req, res){
+    res.sendFile(__dirname + '/introduction.html');
+});
+
+app.get('/calendar.html', function(req, res){
+    res.sendFile(__dirname + '/calendar.html');
+});
+
+
+app.get('/simulation.html', function(req, res){
+    res.sendFile(__dirname + '/simulation.html');
+});
+