docs: Update CHANGELOG for assert_compact_debug_snapshot (#552)

Author: tisonkun

CHANGELOG.md

@@ -4,6 +4,8 @@ All notable changes to insta and cargo-insta are documented here.
 
 ## 1.40.0
 
+- Added support for compact debug snapshots (`assert_compact_debug_snapshot`). #514
+
 - Inline snapshots now use the required number of `#`s to escape the snapshot
   value, rather than always using `###`. This allows snapshotting values which
   themselves contain `###`. If there are no existing `#` characters in the