Update readme about the PHP file in the project

README.md

@@ -131,3 +131,17 @@ Fill in the meta information :
 ### FAQ section
 
 Edit `_data/faq.json` file to add a new Q/A couple object. Plain html e.g. `<br>` or `<a href="">link</a>` is supported
+
+### Contact form
+
+Edit `partials/components/contact-form.html` file to modify the contact form and `src/form/contact-form-handler.php` to modify the form handler.
+
+To test it in a local environment, because there is PHP to execute, you will need to setup a apache vhost with the `dist` folder as the root and the phpmailer library installed.
+Add these lines to the vhost configuration file (here with mailtrap as smtp provider for testing purposes):
+
+```
+SetEnv ASTRO_SMTP_FROM test@astrolabe.test
+SetEnv ASTRO_SMTP_HOSTNAME sandbox.smtp.mailtrap.io
+SetEnv ASTRO_SMTP_USERNAME xxxxx
+SetEnv ASTRO_SMTP_PASSWORD xxxxx
+```