Check on scroll (à la Isabelle)

[Alizter]

Isabelle is able to check on editor scroll, including not checking the proofs that are not in view.

• in [fleche] Auto-check documents on scroll when in lazy mode. #717, we have implemented support for checking document only to the last position scrolled.

Still, skipping Qed. proofs that are not in view remains a TODO.

[ejgallego]

It would be cool if LSP natively provided us with hints for this, as well as for cursor position. Maybe worth opening an issue upstream?

[ejgallego]

See the discussion upstream in microsoft/language-server-protocol#1414 (comment)

[ejgallego]

This is actually implemented by #717 , I'm keeping this issue open for lazy proof checking tho.