add text editor options (font size, on/off suggestions)

A few options to improve the experience of using rgbds-live:

• specify font size; could be on-screen buttons, a field in the "settings" menu and/or keyboard shortcuts (currently the only way to make font size bigger is to live edit the stylesheet in the web browser)
• disable suggestions/autocomplete ; it is good at the beginning but then it is not needed and makes the interface feel slow

Thanks!