Warn about incompatibility with @babel/plugin-transform-react-inline-…

…elements (#1712)

Since there's only the one warning I think it makes more sense to put it at the top where it shows implementing the plugin in `.babelrc`. I also noticed that the full page for the docs on the `@emotion/babel-preset-css-prop` doesn't make any mention of this incompatibility.

Co-authored-by: Mateusz Burzyński <mateuszburzynski@gmail.com>

packages/babel-preset-css-prop/README.md

@@ -20,6 +20,10 @@ yarn add @emotion/babel-preset-css-prop
 
 ## Usage
 
+> Note:
+>
+> This plugin is not compatible with `@babel/plugin-transform-react-inline-elements`. If you use both then your `css` prop styles won't be applied correctly.
+
 **.babelrc**
 
 ```json