Update changelog

Author: adamwathan

CHANGELOG.md

@@ -29,6 +29,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Ensure variants are grouped properly for plugins with order-dependent utilities ([#4273](https://github.com/tailwindlabs/tailwindcss/pull/4273))
 - Resolve purge paths relative to `tailwind.config.js` instead of the current working directory ([#4214](https://github.com/tailwindlabs/tailwindcss/pull/4214))
 - Fix JIT temp file storage when node temp directories are kept on a different drive than the project itself ([#4044](https://github.com/tailwindlabs/tailwindcss/pull/4044))
+- Support border-opacity utilities alongside default `border` utility ([#4277](https://github.com/tailwindlabs/tailwindcss/pull/4277))
 
 ## [2.1.2] - 2021-04-23