Update CHANGES

Author: jonludlam

CHANGES.md

@@ -6,6 +6,7 @@
 - Added a `header` field to the json output (@panglesd, #1314)
 - Added an `extract-code` subcommand to extract code blocks from mld files
   (@panglesd, #1326)
+- Exposed sherlodoc libraries for use in other projects (@jonludlam, #1349)
 
 ### Changed