Add option to "Delay capture" in capture UI

I think the problem in https://github.com/BabylonJS/Spector.js/issues/293#issuecomment-1888014443 could be solved by adding a delay.

If the UI allowed to "Capture in 5.0 seconds" then the user has a chance to click the capture button in the UI, switch to the canvas and then interact with it so it actually redraws the interesting portion when the capture happens.

A similar feature often exists in screenshot tools (as it does in physical cameras); often paired with a visible countdown so the user knows when the capture will happen.

It might also be useful to specify the delay in frames instead. This could also come handy with the "Capture on reload" option.