Add semicolons to JS code sample

Change JS code sample to include semicolons.

BEFORE
```js
var express = require('express')
var app = express()

app.get('/', function (req, res) {
  res.send('Hello World')
})

app.listen(3000)
```

AFTER
```js
var express = require('express');
var app = express();

app.get('/', function (req, res) {
  res.send('Hello World');
});

app.listen(3000);
```