Update CHANGELOG

CHANGELOG.md

@@ -7,6 +7,7 @@ ChangeLog
 - **Update(js):** Redefined customSearch option.
 - **Update(js):** Fixed show footer cannot work bug.
 - **Update(js):** Fixed IE11 transform bug.
+- **Update(export extension):** Fixed export selected bug.
 
 ### 1.13.4