build: use nvm with latest node LTS

.nvmrc

+v18.12.1

package.json

@@ -10,5 +10,8 @@
     "@slidev/cli": "^0.38.2",
     "@slidev/theme-default": "*",
     "@slidev/theme-seriph": "*"
+  },
+  "devDependencies": {
+    "@iconify-json/fa-brands": "^1.0.2"
   }
 }