Destory pdf document to allow for GC to cleanup the document from memory

@@ -334,6 +334,7 @@ class PrintingPlugin extends PrintingPlatform {
         data.toBytes(),
       );
     }
+    t.destroy();
   }
 }
 

@@ -43,6 +43,7 @@ class Settings {
 @JS()
 class PdfJsDocLoader {
   external Future<PdfJsDoc> get promise;
+  external Future<void> destroy();
 }
 
 @anonymous