Update changelog

Author: adamwathan

CHANGELOG.md

@@ -7,7 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-- Add negative spacing values to inset plugin in the `extendedSpacingScale` experiment ([#2358](https://github.com/tailwindlabs/tailwindcss/pull/2368))
+- Add negative spacing values to inset plugin in the `extendedSpacingScale` experiment ([#2358](https://github.com/tailwindlabs/tailwindcss/pull/2358))
+- Add `future` section to config stubs ([#2372](https://github.com/tailwindlabs/tailwindcss/pull/2372), [3090b98](https://github.com/tailwindlabs/tailwindcss/commit/3090b98ece766b1046abe5bbaa94204e811f7fac))
 
 ## [1.8.8] - 2020-09-11