feat: allow user to customize favicon (#47)

* feat: add basic custom favicon feature

* add auto-switch icon

* revert to the original setting `false`

src/types/config.ts

@@ -9,6 +9,15 @@ export type SiteConfig = {
     enable: boolean
     src: string
   }
+
+  favicon: {
+    enable: boolean
+    size: string
+    src: {
+      light: string
+      dark: string
+    }
+  }
 }
 
 export enum LinkPreset {