add explanations of how RibsCronBundle works

Author: Piou-piou

README.md

@@ -1,2 +1,39 @@
 # RibsCronBundle
 RibsCronBundle is a bunlde to use cron via curl a url of you website with cron based time
+
+## Create you first method called by ribs_cron
+
+Craete a new Controller class and extends it to RibsCronController.
+Create a method with the name you want like this example : 
+```PHP
+<?php
+
+namespace App\Controller;
+
+use PiouPiou\RibsCronBundle\Controller\RibsCronController;
+
+class TestCronController extends RibsCronController
+{
+    public function testCronCall()
+    {
+        // do action called by /ribs-cron
+    }
+}
+```
+
+Now to make this method called by /ribs-cron url you must add it to ribs_cron.yaml config file like this : 
+```YML
+parameters:
+  data_directory: '%kernel.project_dir%/data/'
+  ribs_cron:
+    testCronCall: "* * * * *"
+```
+
+After that each time you have in your crontab file a curl to /ribs-cron url testCronCall method will be executed each minute.
+Parameters in quote run like standard cron time system.
+
+ ## How to call your cron url at any time with external url
+ 
+ In you .env file you can add two parameters : 
+IP_CRON_EXTERNAL to add external IP that can call your cron
+IP_CRON_INTERNAL= internals IPS of the server that can call your cron