🔧(frontend) configure Material Icons and Symbols

Robin chose to adopt Material Design icons, inspired by NVasse’s commit on
Fichier. This sets up the required CSS to easily use Material Icons throughout
the application.

Eventually, all icons in the app will be replaced with Material ones. For now,
the setup is only used in the recording UI refactor.

src/frontend/package.json

@@ -13,6 +13,8 @@
     "check": "prettier --check ./src"
   },
   "dependencies": {
+    "@fontsource-variable/material-symbols-outlined": "5.2.30",
+    "@fontsource/material-icons-outlined": "5.2.6",
     "@livekit/components-react": "2.9.13",
     "@livekit/components-styles": "1.1.6",
     "@livekit/track-processors": "0.6.1",