docs: add cssnano 5 release notes

site/blog/2021-03-31-cssnano-5.md

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+---
+slug: cssnano-5-release-notes
+title: cssnano 5 release
+---
+
+We have released a new version of cssnano.
+
+## Major changes
+
+* requires Node >= 10.13
+* PostCSS 8 API, so cssnano 5 does not emit warnings when running under PostCSS 8 
+* updated to SVGO 2, fixing many SVG minification bugs
+* updated css-value-parser and css-selector-parser, fixing many bugs
+
+### Upgrade notes
+If you use the cssnano JavaScript API, you need to change your code:
+
+* Replace `cssnano.process()` with `cssnano().process()` (notice the `()` after `cssnano`)
+
+* cssnano specific options go into the  options go to cssnano instead of process
+
+```
+cssnano(cssnanoOptions).process(postcssOptions)
+```
+
+## Bug fixes
+
+* fix improperly discarding `@font-face` declarations [#726](https://github.com/cssnano/cssnano/issues/726)
+* partially fix some isues where cssnano did not combine rules when used together with `postcss-nested` [#1004](https://github.com/cssnano/cssnano/issues/1004)
+* fix `translate3d()` minification [#920](https://github.com/cssnano/cssnano/issues/920)
+* fix minification of values starting with `e` [#589](https://github.com/cssnano/cssnano/issues/958), [#984](https://github.com/cssnano/cssnano/issues/984)
+* fix minification of percentage vaalues [#962](https://github.com/cssnano/cssnano/issues/962), [#957](https://github.com/cssnano/cssnano/issues/957)
+* fix minification of `aspect-ratio` [#963](https://github.com/cssnano/cssnano/issues/963)
+* fix merging of `@supports` rules [#974](https://github.com/cssnano/cssnano/issues/974)
+* fix sorting of longhand and shorthand properties [#535](https://github.com/cssnano/cssnano/issues/535)
+* remove vulnerable dependency and always warn with bad SVG input [#1034](https://github.com/cssnano/cssnano/pull/1034)