Update CHANGELOG.md

Author: bradlc

CHANGELOG.md

@@ -24,6 +24,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Don't stop watching atomically renamed files ([#9173](https://github.com/tailwindlabs/tailwindcss/pull/9173))
 - Re-use existing entries in the rule cache ([#9208](https://github.com/tailwindlabs/tailwindcss/pull/9208))
 - Don't output duplicate utilities ([#9208](https://github.com/tailwindlabs/tailwindcss/pull/9208))
+- Fix `fontFamily` config TypeScript types ([#9214](https://github.com/tailwindlabs/tailwindcss/pull/9214))
 
 ## [3.1.8] - 2022-08-05