docs: add xls to list of package keywords

Author: ghiscoding

packages/excel-builder-vanilla/package.json

@@ -5,6 +5,7 @@
   "keywords": [
     "excel",
     "javascript",
+    "xls",
     "xlsx",
     "spreadsheet"
   ],
@@ -67,4 +68,4 @@
     "typescript": "^5.7.3",
     "vite": "^6.0.11"
   }
-}
+}