Update README.md

Author: chrisrowe

README.md

@@ -33,6 +33,8 @@ module.exports = {
 
 With zero configuration, it will generate grids from 1 to 12 columns in size, no gap sizes, and `responsive` variants for each new utility.
 
+## Classes
+
 The plugin generates the following sets of classes:
 
 - `.grid` for setting `display: grid` on an element
@@ -49,6 +51,8 @@ It's not really practical to expose all of the power of CSS Grid through utiliti
 
 ---
 
+### Credit
+
 This repo was originally isolated from [https://github.com/tailwindcss/plugin-examples](https://github.com/tailwindcss/plugin-examples) to publish to npm. Credit and thanks to [https://github.com/adamwathan](@adamwathan)
 
 [View original demo](https://tailwindcss.github.io/plugin-examples/#css-grid)