Update CHANGELOG.md

Co-authored-by: Samuel Williams <samuel.williams@oriontransfer.co.nz>

CHANGELOG.md

@@ -22,7 +22,7 @@ All notable changes to this project will be documented in this file. For info on
 - `SERVER_PROTOCOL` is now a required key, matching the HTTP protocol used in the request.
 - `rack.hijack?` (partial hijack) and `rack.hijack` (full hijack) are now independently optional.
 - `rack.hijack_io` has been removed completely.
-- rack.early_hints is now officially supported as an optional feature (already implemented by Unicorn, Puma, and Falcon).
+- `rack.early_hints` is added as an optional feature for sending `103 Early Hints` headers.
 
 ### Removed