add changelog entry for button classes (#1976)

* add changelog entry

* prettier

docs/pages/resources/changelog.md

@@ -17,6 +17,7 @@ New versions of Shoelace are released as-needed and generally occur when a criti
 - Fixed a bug in `<sl-split-panel>` that caused it not to recalculate it's position when going from being `display: none;` to its original display value. [#1942]
 - Fixed a bug in `<dialog>` where when it showed it would cause a layout shift. [#1967]
 - Fixed a bug in `<sl-tooltip>` that allowed unwanted text properties to leak in [#1947]
+- Fixed a bug in `<sl-button-group>` classes [#1974]
 
 ## 2.15.0