fix headings

Author: Rich-Harris

packages/site-kit/src/lib/markdown/utils.ts

@@ -15,7 +15,7 @@ export const SHIKI_LANGUAGE_MAP = {
 };
 
 export function is_in_code_block(body: string, index: number) {
-	const code_blocks = [...body.matchAll(/```.*\n(.|\n)+```/gm)].map((match) => {
+	const code_blocks = [...body.matchAll(/(`{3,}).*\n(.|\n)+?\1/gm)].map((match) => {
 		return [match.index ?? 0, match[0].length + (match.index ?? 0)] as const;
 	});