Add formerly-missing changelog entry for lib, associated with the changes in #706

Author: nedtwigg

CHANGES.md

@@ -10,6 +10,8 @@ This document is intended for Spotless developers.
 We adhere to the [keepachangelog](https://keepachangelog.com/en/1.0.0/) format (starting after version `1.27.0`).
 
 ## [Unreleased]
+### Added
+* Exposed new methods in `GitRatchet` to support faster ratcheting in the maven plugin ([#706](https://github.com/diffplug/spotless/pull/706)).
 
 ## [2.7.0] - 2020-09-21
 ### Added