feat: document how to contribute

Signed-off-by: QuentinN42 <quentin@lieumont.fr>

README.md

@@ -2,3 +2,21 @@
 
 Create a sample website from a json.
 Read the `config.json` file to configure the website.
+
+## How to add my website ?
+
+1. Fork this repository.
+2. Add this json in the `config.json` file.
+
+    ```json
+    {
+        "url": "https://TODO.fr",
+        "image": "./static/TODO.png",
+        "name": "TODO",
+        "description": "TODO"
+    }
+    ```
+
+3. Add the image in the `static` folder.
+4. Commit and push.
+5. Create an MR on the `master` branch.