Validate if opts has unknown attributes.

import { Denops } from "../mod.ts";
import { builtinOpts, parse, validateOpts } from "./mod.ts";

export async function main(denops: Denops): Promise<void> {
  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);
}