fix the issue that CSS cannot customize background (#3854)

* fixed the issue that css background cannot be used

* update logs

* fix logs

src/services/types.d.ts

@@ -779,6 +779,9 @@ interface IVergeConfig {
     success_color?: string;
     font_family?: string;
     css_injection?: string;
+    background_image?: string;
+    background_blend_mode?: string;
+    background_opacity?: number;
   };
   auto_close_connection?: boolean;
   auto_check_update?: boolean;