Completed overview documentation

Author: apetenchea

docs/overview.rst

@@ -38,3 +38,25 @@ Here is an example showing how **python-arango-async** client can be used:
             student_names = []
             async for doc in cursor:
                 student_names.append(doc["name"])
+
+You may also use the client without a context manager, but you must ensure to close the client when done:
+
+.. code-block:: python
+    from arangoasync import ArangoClient
+    from arangoasync.auth import Auth
+
+    client = ArangoClient(hosts="http://localhost:8529")
+    auth = Auth(username="root", password="passwd")
+    sys_db = await client.db("_system", auth=auth)
+
+    # Create a new database named "test".
+    await sys_db.create_database("test")
+
+    # Connect to "test" database as root user.
+    db = await client.db("test", auth=auth)
+
+    # List all collections in the "test" database.
+    collections = await db.collections()
+
+    # Close the client when done.
+    await client.close()