Update CHANGELOG.md

Author: MaySoMusician

CHANGELOG.md

@@ -15,6 +15,9 @@ _Please add entries here for your pull requests that are not yet released._
 - Upgrades React-Rails' embedded react to v18.2.0. Uses node polyfill plugin & fast-text-encoder for SSR text encoding. #1290
 - If using Webpacker/Shakapacker, requires upgrading to Shakapacker v7 #1274 and #1285
 
+#### Added
+- Added option to replace `null`s in props with `undefined` via `config.react.null_to_undefined_props` in `config/application.rb` #1293
+
 #### Changed
 - The `react:component` generator now generates a function component by default #1271