✨ Added a background image input

Added an input in the advanced options for a background image. Also removed an unused import from my previous commit and changed the margin on the header bar to padding instead.

src/tools/types.ts

@@ -7,6 +7,7 @@ export interface Settings {
   favicon?: string;
   primary_color?: string;
   secondary_color?: string;
+  background?: string;
 }
 
 export interface Config {