Add usage example

(#AdventOfPureCode 1)

README.md

@@ -9,3 +9,38 @@
   </img>
 </a>
 
+## Example usage:
+
+```purescript
+import React.Basic.DOM as R
+import React.Basic.Hooks as React
+import React.Basic.Emotion as E
+
+myUnstyledDiv :: JSX
+myUnstyledDiv = React.element R.div' 
+    { children: [ R.text "I have no style :(" ] 
+    }
+
+myStyledDiv :: JSX
+myStyledDiv = E.element R.div' 
+  { className: "stylish-div" 
+  , css: E.css 
+      { color: E.str "rebeccapurple"
+      , padding: E.px 4
+      }
+  } 
+```
+
+Note that you need to use the apostrophised variants of react components from `React.Basic.DOM` since these represent the raw `ReactComponent`s that `Emotion` expects to work with.
+
+## Going beyond what `style` can give you
+
+Emotion allows you to define real CSS rules rather than only inline styles.
+Here's an example of something you can't do with inline styles:
+
+```purescript
+myStyle :: Style
+myStyle = E.css 
+  { "&:hover": E.nested (E.css { background: E.str "#fed" })
+  }
+```