fix: isCheckout is not included in fullsnapshot event (rrweb-io#1141)

* fix: isCheckout is not included in fullsnapshot event

* add change log

Author: YunFeng0817

.changeset/stupid-ghosts-help.md

@@ -0,0 +1,5 @@
+---
+'rrweb': patch
+---
+
+Fix: isCheckout is missed in all fullsnapshot events

packages/rrweb/src/record/index.ts

@@ -398,6 +398,7 @@ function record<T = eventWithTime>(
           initialOffset: getWindowScroll(window),
         },
       }),
+      isCheckout,
     );
     mutationBuffers.forEach((buf) => buf.unlock()); // generate & emit any mutations that happened during snapshotting, as can now apply against the newly built mirror