Fix formatting of README file

Author: bertdeblock

README.md

@@ -4,7 +4,8 @@ This is the blueprint that is used to generate a **new** Ember app using [Vite](
 
 If you have an existing app that you would like to upgrade to use Vite consider using the [ember-vite-codemod](https://github.com/mainmatter/ember-vite-codemod)
 
-## Usage
+## Usage
 
+```
 pnpm dlx ember-cli@latest app my-app-name -b @ember/app-blueprint --pnpm
-
+```