Update CHANGELOG

Author: egiurleo

Diff for: CHANGELOG.md

@@ -9,6 +9,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/) a
 ### Changed
 
 - Fixed the AST output by adding blocks to `Command` and `CommandCall` nodes in the `FieldVisitor`.
+- The `Elsif` node has been folded into `IfNode`. A `keyword` field has been added to `IfNode` specifying if the node represents an `if` or `elsif`.
 
 ## [6.0.1] - 2023-02-26