Change background color of the Project Notes editor

As (at least) the Windows text cursor uses the inverted color of the hovered area, I think it would be good to change the background color of the Project Notes from 127,127,127 or use another cursor icon for it. The cursor is invisible for me right now.

Start by locating the Project Notes editor in the LMMS codebase and reproduce the invisible text cursor on Windows. Inspect the editor's background and cursor handling; the issue is done when the cursor is visible against the Project Notes background without reducing editor usability.

Written by the indexing model from the issue text.