Host mode should have a button for switching to notes view

[taneltm]

Notes view is opened by pressing the S key on the keyboard.

On a mobile device or tablet, one could theoretically use the virtual keyboard, but on my android phone the only way to bring up the virtual keyboard is by clicking on a text input field.

The only way to access the notes page is by typing the URL manually.

I suggest that the host mode should have a button for opening the notes view.

[lilijreey]

@taneltm you are right. There is failed if you direct type the notes URL on a mobile, the web server can not handle file path 'reveal.js/plugin/notes/notes.html'