Configure inline diagnostics delay (preset 350ms)

[ok-nick]

Hi, it would be nice if we could configure the inline diagnostics delay found here:

helix/helix-view/src/handlers/diagnostics.rs

Line 24 in 101a74b

const TIMEOUT: Duration = Duration::from_millis(350);

I'm currently using end of line diagnostics with inline diagnostics on the cursor line and it would be nice to display inline diagnostics instantly. I'm assuming the reason this delay was added was to address performance concerns when using the other-lines setting?

[poliorcetics]

IIRC it's also to avoid flickering when quickly scrolling through lines

[llakala]

I'd like this for a different reason: to put a longer delay. While typing a new line, I get constant errors even though I haven't finished typing yet. I'd want a delay of 2-3 seconds without keystrokes before the error actually popped up.