feat: add built-in Mercure support (#89)

* feat: Mercure support

* feat: add native Mercure support

* improvements

* feat: add Mercure UI

* fix: typo

* finish

docs/build.md

@@ -17,6 +17,8 @@ For instance, use the following command to use the `master` branch of Symfony:
 
 ## Customizing the Server Name
 
-Use the `SERVER_NAME` environment variable to define your custom server name.
+Use the `SERVER_NAME` environment variable to define your custom server name(s).
 
-    $ SERVER_NAME=symfony.wip docker-compose up --build
+    $ SERVER_NAME="symfony.wip, caddy:80" docker-compose up --build
+
+If you use Mercure, keep `caddy:80` in the list to allow the PHP container to request the caddy service.

docs/extra-services.md

@@ -6,4 +6,5 @@ the recipe will automatically modify the `Dockerfile` and `docker-compose.yml` t
 The currently supported packages are:
 
 * `symfony/orm-pack`: install a PostgreSQL service
+* `symfony/mercure-bundle`: use the Mercure.rocks module shipped with Caddy
 * `symfony/messenger`: install a RabbitMQ service