docs: changelog

CHANGELOG.md

@@ -1,10 +1,11 @@
 ## Changelog
 
-### 3.1.0 (pre-release)
+### 3.1.0 
 * feat: parse `'transparent'` as black with 0% opacity - resolves [#280](https://github.com/gka/chroma.js/issues/280)
 * make it easier to access colorbrewer palette names - resolves [#314](https://github.com/gka/chroma.js/issues/314)
 * docs: explain differences to official colorbrewer scales - resolves [#316](https://github.com/gka/chroma.js/issues/316)
 * fix: correct parsing of modern css colors with percentage alpha - resolves [#297](https://github.com/gka/chroma.js/issues/297)
+* fix: css output for hue-less colors in lch() and oklch() - resolves [#357](https://github.com/gka/chroma.js/issues/357)
 
 ### 3.0.0
 * 🎉 NEW: Add support for modern CSS color spaces. This means you can now export and parse CSS colors in `lab()`, `lch()`, `oklab()`, `oklch()` space.