feat: playground add submenu

src/utils/read-html.ts

@@ -0,0 +1,15 @@
+export default function readHtmlContent(file: File): Promise<string> {
+  return new Promise((resolve, reject) => {
+    const reader = new FileReader();
+    reader.onload = function (e: any) {
+      const fileContent = e.target.result;
+
+      const parser = new DOMParser();
+      const doc = parser.parseFromString(fileContent, 'text/html');
+      const textContent = doc.body.textContent || '';
+      resolve(textContent);
+    };
+    reader.onerror = (error) => reject(error);
+    reader.readAsText(file);
+  });
+}