[Feature] update preview on CursorHold

[gbcreation]

Hi! Thank for this very useful plugin.

When navigating with j/k, the preview window is updated immediately. When holding down j/k to navigate quickly among files, it makes the navigation lag.

Could you please add an option to update the preview only on CursorHold?

[b0o]

I would happily accept a PR for this! Should be simple to add a config option and use it to determine what autocommand to use.