add dev info

docs/developer-info.md

@@ -0,0 +1,17 @@
+### Backend Apps
+
+If you planing to extend the Backend with you own apps (api endpoints),
+just add you app folder in **ffplayout/apps**.
+
+If you planing to us a DB, put a **db.py** file in your app. With this `Class`:
+
+```
+class Connector:
+    config = {
+        'default': {
+            'ENGINE': 'django.db.backends.sqlite3',
+            'NAME': os.path.join(BASE_DIR, 'db-name.sqlite3'),
+        }
+    }
+
+```