Update changelog

Author: gmazzap

CHANGELOG.md

@@ -4,6 +4,8 @@
 - Fix bug in `Psr4Sniff` when class has not namespace.
 - Allow @wp-hook ignore of return type for private and protected methods
 - Only check public accessors (by default)
+- Fix bug in checking return type
+- Allow filters callbacks to return `null` on purpose
 
 ## 0.11.0
 - Fix false positive in `ReturnTypeDeclarationSniff` with nullable types.