Validate if opts has unknown attributes.

import type { Entrypoint } from "https://deno.land/x/denops_std@v6.5.1/mod.ts";
import { builtinOpts, parse, validateOpts } from "https://deno.land/x/denops_std@v6.5.1/argument/mod.ts";

export const main: Entrypoint = async (denops) => {
  const args = [
    "++enc=sjis",
    "++ff=dos",
    "-f",
    "--foo=foo",
    "--bar=bar",
    "--bar=baz",
    "hello",
    "world",
  ];
  const [opts, _flags, residues] = parse(args);

  validateOpts(opts, ["enc", "ff"]);

  // Or use `builtinOpts` to validate Vim's builtin `++opts`
  validateOpts(opts, builtinOpts);
}