adapt to sglang v0.5.2rc1 on dcu

sgl-router/py_src/sglang_router/__init__.py

@@ -0,0 +1,7 @@
+# a lightweihgt wrapper on router with argument type and comments
+# no wrapper on policy type => direct export
+from sglang_router.router import Router
+from sglang_router.version import __version__
+from sglang_router_rs import PolicyType
+
+__all__ = ["Router", "PolicyType", "__version__"]