docs: update README.md

README.md

@@ -4,4 +4,17 @@ This repository is hosting Symfony Flex Recipes for Sitepark
 
 You can look into the [Symfony documentation](https://github.com/symfony/recipes#creating-recipes) for more information about the recipe format.
 
-See also [Create an Index to the Recipes](https://symfony.com/doc/current/setup/flex_private_recipes.html#create-an-index-to-the-recipes) to add more recipes
+See also [Create an Index to the Recipes](https://symfony.com/doc/current/setup/flex_private_recipes.html#create-an-index-to-the-recipes) to add more recipes
+
+Please add the following entry to your `composer.json` to use the recipes.
+
+```json
+"extra": {
+    "symfony": {
+        "endpoint": [
+           "https://api.github.com/repos/sitepark/symfony-recipes/contents/index.json?ref=flex/main",
+           "flex://defaults"
+        ]
+    }
+}
+```