Add a "Run the Application" section in the Readme

Author: jmini

Readme.adoc

@@ -24,4 +24,15 @@ UNBLU_PASSWORD=hello-im-some-unblu-admin-user-password
 MIDDLEWARE_URL=https://where.my.middleware.is.running
 WEBHOOK_SECRET=a-very-secret-key
 BOT_SECRET=another-very-secret-key
-----
+----
+
+=== Run the Application
+
+Run the following command in a terminal window:
+
+[source,bash]
+----
+./gradlew bootRun
+----
+
+Your middleware application is running on port http://localhost:8080