fix: update minimal MultiAgentRouter example and documentation

examples/multi_agent/mar/multi_agent_router_minimal.py

@@ -1,6 +1,6 @@
-from swarms import Agent, MultiAgentRouter
+from swarms import Agent
+from swarms.structs.swarm_router import SwarmRouter
 
-if __name__ == "__main__":
 agents = [
     Agent(
         agent_name="Researcher",
@@ -14,6 +14,12 @@ if __name__ == "__main__":
     ),
 ]
 
-    router = MultiAgentRouter(agents=agents)
+router = SwarmRouter(
+    name="multi-agent-router-demo",
+    description="Routes tasks to the most suitable agent",
+    agents=agents,
+    swarm_type="MultiAgentRouter"
+)
 
-    result = router.route_task("Write a function that adds two numbers")
+result = router.run("Write a function that adds two numbers")
+print(result)