Auto refresh in the ESP_Code Dashboard

The Dashboard.h for the ESP_Code has no auto refresh.

I suggest to add:
```
<head>
      ...
        <script>
            function autoRefresh() {
                window.location = window.location.href;
            }
            setInterval('autoRefresh()', 20000);
        </script>
      ...
</head>
```
So it auto refresh every 20 sec.
