Add changelog markers, remove unreleased version changelog

Author: krassowski

CHANGELOG.md

@@ -1,11 +1,6 @@
 # Changelog
 
-## Unreleased
-
-**Jupyterlab extension**
-
-- Add "Go to cell" option in dialog when formatting fails;
-- Add "suppressFormatterErrorsIFFAutoFormatOnSave" config;
+<!-- <START NEW CHANGELOG ENTRY> -->
 
 ## 2.2.1 2023-05-21
 
@@ -17,6 +12,8 @@
 
 - Actually support python>=3.7,<3.9 properly, courtesy of pdhall99;
 
+<!-- <END NEW CHANGELOG ENTRY> -->
+
 ## 2.2.0 Skipped
 
 ## 2.1.0 2023-05-08