feat: 页码先加载3页处理

src/pages/explain/index.vue

@@ -101,7 +101,7 @@ export default {
       if (this.numPages == 0) {
         return;
       }
-      this.loadedPages = this.numPages > 1 ? 1 : 1;
+      this.loadedPages = this.numPages > 3 ? 3 : this.numPages;
     },
 
     ///截取文件