docs: update favicon

docs/.vitepress/theme/index.ts

@@ -1,9 +1,17 @@
+import type { Theme } from 'vitepress'
 import DefaultTheme from 'vitepress/theme'
 
 import './vars.css'
 import './overrides.css'
 import 'uno.css'
 
-export default {
-  ...DefaultTheme,
+const config: Theme = {
+  extends: DefaultTheme,
+  enhanceApp({ app }) {
+    app.config.globalProperties.$spec = {
+      version: '2.0',
+    }
+  },
 }
+
+export default config