Function start_flash 

fn start_flash(
    api: &dyn WindowsApi,
    state: ClientState,
    palette: &ConsolePalette,
    last: &mut Option<CONSOLE_CHARACTER_ATTRIBUTES>,
) -> Instant

Paint the action-feedback flash and return the deadline at which the steady-state should be restored.

Arguments

• api - The Windows API implementation to use.
• state - The just-applied ClientState.
• palette - The available colors.
• last - Most recently painted color; updated in place.

Returns

The [tokio::time::Instant] the flash should be cleared at.