Update 01-basic-usage.md

Hello,

I add the `php composer.phar dump-autoload` command explicity because i didn't find it on the doc like this.

Cheers 😉

doc/01-basic-usage.md

@@ -241,8 +241,14 @@ be in your project root, on the same level as `vendor` directory is. An example
 filename would be `src/Foo.php` containing an `Acme\Foo` class.
 
 After adding the [`autoload`](04-schema.md#autoload) field, you have to re-run
-[`dump-autoload`](03-cli.md#dump-autoload) to re-generate the
-`vendor/autoload.php` file.
+this command : 
+
+```sh
+php composer.phar dump-autoload
+```
+
+This command will re-generate the `vendor/autoload.php` file.
+See the [`dump-autoload`](03-cli.md#dump-autoload) section for more informations.
 
 Including that file will also return the autoloader instance, so you can store
 the return value of the include call in a variable and add more namespaces.