docs: install headings

Author: vgarciaf

README.md

@@ -12,12 +12,14 @@ composer require --dev descom/dev
 
 ### PHP CS Fixer
 
-Using setup.sh.
+#### Using setup.sh
 
 ```bash
 bash <(curl -Ls https://raw.githubusercontent.com/descom-es/php-dev/master/setup.sh)
 ```
 
+#### Manually
+
 Install php-cs-fixer.
 
 ```bash