Add SVG icon definition for YouTube summarization feature in layout

templates/layout.html

@@ -162,5 +162,18 @@
         document.getElementById('darkModeToggle').addEventListener('click', toggleDarkMode);
         document.getElementById('darkModeToggleMobile').addEventListener('click', toggleDarkMode);
     </script>
+    <svg>
+      <defs>
+      <symbol id="icon-summarizeYouTube"  viewBox="0 0 48 48">
+        <linearGradient id="PgB_UHa29h0TpFV_moJI9a" x1="9.816" x2="41.246" y1="9.871" y2="41.301" gradientUnits="userSpaceOnUse">
+                <stop offset="0" stop-color="#f44f5a"/><stop offset=".443" stop-color="#ee3d4a"/>
+                <stop offset="1" stop-color="#e52030"/>
+        </linearGradient>
+        <path fill="url(#PgB_UHa29h0TpFV_moJI9a)" d="M45.012,34.56c-0.439,2.24-2.304,3.947-4.608,4.267C36.783,39.36,30.748,40,23.945,40	c-6.693,0-12.728-0.64-16.459-1.173c-2.304-0.32-4.17-2.027-4.608-4.267C2.439,32.107,2,28.48,2,24s0.439-8.107,0.878-10.56	c0.439-2.24,2.304-3.947,4.608-4.267C11.107,8.64,17.142,8,23.945,8s12.728,0.64,16.459,1.173c2.304,0.32,4.17,2.027,4.608,4.267	C45.451,15.893,46,19.52,46,24C45.89,28.48,45.451,32.107,45.012,34.56z"/><path d="M32.352,22.44l-11.436-7.624c-0.577-0.385-1.314-0.421-1.925-0.093C18.38,15.05,18,15.683,18,16.376	v15.248c0,0.693,0.38,1.327,0.991,1.654c0.278,0.149,0.581,0.222,0.884,0.222c0.364,0,0.726-0.106,1.04-0.315l11.436-7.624	c0.523-0.349,0.835-0.932,0.835-1.56C33.187,23.372,32.874,22.789,32.352,22.44z" opacity=".05"/>
+        <path d="M20.681,15.237l10.79,7.194c0.689,0.495,1.153,0.938,1.153,1.513c0,0.575-0.224,0.976-0.715,1.334	c-0.371,0.27-11.045,7.364-11.045,7.364c-0.901,0.604-2.364,0.476-2.364-1.499V16.744C18.5,14.739,20.084,14.839,20.681,15.237z" opacity=".07"/>
+        <path fill="#fff" d="M19,31.568V16.433c0-0.743,0.828-1.187,1.447-0.774l11.352,7.568c0.553,0.368,0.553,1.18,0,1.549	l-11.352,7.568C19.828,32.755,19,32.312,19,31.568z"/>
+      </symbol>
+      </defs>
+    </svg>
 </body>
 </html>