Output of scripts at the input field displayed placeholder style

[moretticb]

The output of scripts on the input field upon keystrokes (#53) is currently more text concatenated to current user's input. Although there is some (complex) event management to clear current output when typing, or moving the cursor, it would be nice to have such an output displayed as a separate UI element. Perhaps something like a placeholder text: not selectable, not concatenated to the original user input.

This would simplify event management of keystrokes, improve user experience, and make this feature more robust.