Update changelog

Author: adamwathan

CHANGELOG.md

@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Add `cursor-help` by default ([#3199](https://github.com/tailwindlabs/tailwindcss/pull/3199))
 - Add support for a `tailwind.config.cjs` file in Node ESM projects ([#3181](https://github.com/tailwindlabs/tailwindcss/pull/3181))
 - Fix issue where `theme()` didn't work with colors defined as functions ([#2919](https://github.com/tailwindlabs/tailwindcss/pull/2919))
+- Enable `dark` variants by default for color opacity utilities ([#2975](https://github.com/tailwindlabs/tailwindcss/pull/2975))
 
 ## [2.0.2] - 2020-12-11