Documented CORS

README.md

     "recipients": [
         "you@example.tld",
         "someone.else@example.com"
-    ]
+    ],
+    "formOrigin": "https://example.tld"
 }
 ```
 
 
 The `recipients` server is an array containing the e-mail addresses any message sent via the form will be sent to. Just write down the form's recipient(s)'s addresse(s).
 
+Finally, the `formOrigin` part is a string containing the origin of the page you'll include the contact form into. This allows SMAM to work with the [Cross-Origin Resource Sharing (CORS)](https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS) security most browser use. For more info on how to fill this field, and what is an origin, please give a look at [the MDN's definition](https://developer.mozilla.org/en-US/docs/Glossary/origin).
+
 ## Templating
 
 Each e-mail sent by the form follows a template described in `template.pug` (it's [Pug](pugjs.org/)). If you want to change the way the e-mails you receive are displayed in your mailbox, just edit it! You don't even need to restart the server aftewards :smile: