Pretty-print the expression in widget mode

When you have longer expressions, the text and widget modes render very differently. It would be very nice if we could also pretty-print in the widget mode. Here’s an example:

example : ∀ n : ℕ, to_string n ≠ "hello" :=
begin
    intro n, dsimp [to_string, has_to_string.to_string, repr, has_repr.repr, nat.repr, nat.to_digits],
    delta nat.to_digits,
    -- put your cursor here
end

The top state is rendered using widget mode, the bottom one is just text, but they both refer to the same proof state.

[EdAyers]

The vscode extension does not need to be adjusted

[EdAyers]

So this issue should be moved to the lean repo or mathlib, it’s not a vscode problem