String to extract from.

import { extract } from "https://deno.land/std@0.145.0/encoding/front_matter.ts";
import { assertEquals } from "https://deno.land/std@0.145.0/testing/asserts.ts";

const { attrs, body, frontMatter } = extract<{ title: string }>("---\ntitle: Three dashes marks the spot\n---\n");
assertEquals(attrs.title, "Three dashes marks the spot");
assertEquals(body, "");
assertEquals(frontMatter, "---\ntitle: Three dashes marks the spot\n---\n");