add custom field option

index.ts

@@ -247,6 +247,15 @@ function formatCard(data: YGOProCardLike): YGOProCard {
       'https://cdn02.moecube.com:444/images/ygopro-images-zh-CN/') +
     data.id.toString() +
     (process.env.YGOPRO_PIC_URL_SUFFIX || '.jpg');
+  if (process.env.FIELDS) {
+    const fields = new Set(process.env.FIELDS.split(','));
+    // keep only the fields specified
+    for (const key of Object.keys(result)) {
+      if (!fields.has(key)) {
+        delete result[key];
+      }
+    }
+  }
   return result as YGOProCard;
 }