Only activate partytown if necessary

src/utils/frontmatter.mjs

@@ -0,0 +1,11 @@
+import getReadingTime from 'reading-time';
+import { toString } from 'mdast-util-to-string';
+
+export function remarkReadingTime() {
+	return function (tree, { data }) {
+		const text = toString(tree);
+		const readingTime = Math.ceil(getReadingTime(text).minutes);
+
+		data.astro.frontmatter.readingTime = readingTime;
+	};
+}