feat: upgrade postcss to 8.x

BREAKING CHANGE: upgrade postcss to 8.x

Co-authored-by: Edward Elric <[email protected]>
Co-authored-by: Ward Peeters <[email protected]>

Author: 3 people

README.md

@@ -241,7 +241,7 @@ Type: `object`
 
 [`ctx`](https://github.com/michael-ciniawsky/postcss-load-config#context) argument for PostCSS config file.
 
-Note: Every keys you pass to `config.ctx` will be available under `options` inside
+Note: Every key you pass to `config.ctx` will be available under `options` inside
 the postcss config.
 
 ```js