import { op } from "https://deno.land/x/ddc_vim@v4.3.1/deps.ts";
const { previewwindow } = op;
Identifies the preview window. Only one window can have this option
set. It's normally not set directly, but by using one of the commands
:ptag, :pedit, etc.
(default off)
not available when compiled without the +quickfix feature