Update release notes

Author: lszomoru

release-notes/v1_100.md

@@ -184,6 +184,9 @@ Copilot now has an LLM tool to run notebook cells which will allow the agent to
 
 ## Source Control
 
+### Quick diff decorations for staged changes
+
+To address a long-time feature request, this milestone we have added quick diff editor decorations for staged changes. These new quick diff decorations provide better visibility to the staged changes as well as enable editor actions like "Unstage Changes" and "Unstage Selected Ranges" that were previously available only in the diff editor. You can customize the color of the staged changes quick diff decorations using the following theme tokens: `editorGutter.addedSecondaryBackground`, `editorGutter.modifiedSecondaryBackground`, `editorGutter.deletedSecondaryBackground`. If you do not want to see quick diff decorations for staged changes, you can hide them using the "Diff Decorations" submenu that is available in the editor gutter context menu.
 
 ## Terminal