Rename cover image file if not jpg extension

src/main.ts

@@ -149,6 +149,13 @@ export default class BookTrackerPlugin extends Plugin {
 			maintainAspectRatio: true,
 		});
 
+		if (file.extension !== "jpg") {
+			await this.app.fileManager.renameFile(
+				file,
+				file.path.replace(/\.[^.]+$/, ".jpg")
+			);
+		}
+
 		return file;
 	}