fix(core): update

ts/smartpdf.plugins.ts

@@ -14,6 +14,7 @@ import * as smartunique from '@pushrocks/smartunique';
 export { smartfile, smartpromise, smartpuppeteer, smartunique, smartnetwork };
 
 // thirdparty
+import pdfMerger from 'pdf-merger-js';
 import express from 'express';
 
-export { express };
+export { pdfMerger, express };