Support for placing and showing the cursor

[nojb]

Is it possible to specify where the terminal cursor should be placed, as well as showing it? I tried using Notty.show_cursor but didn't seem to work.

What I had in mind is a special combinator cursor : A.attr -> I.image that would have size 1x1 but that would have a special behaviour when overlaid over an image already containing cursor: any underlying cursor would be removed.

[nojb]

(This is useful for terminal UIs such as text fields, etc.)