Add example of using @web_endpoint with lifecycle class (#472)

07_web_endpoints/basic_web.py

@@ -0,0 +1,33 @@
+import modal
+from modal import web_endpoint
+
+stub = modal.Stub(name="example-lifecycle-web")
+
+# Hello world!
+#
+# This is as simple as it gets. A GET endpoint which
+# returns a string.
+
+
+@stub.function()
+@web_endpoint()
+def hello():
+    return "Hello world!"
+
+
+# Lifecycle-based.
+#
+# Web endpoints can be methods on a [lifecycle class](/docs/guide/lifecycle-functions#container-lifecycle-functions-and-parameters).
+# This example will only set the `val` instance variable once, on container startup.
+# But note that they don't need the [`modal.method`](/docs/reference/modal.method#modalmethod) decorator.
+
+
+@stub.cls()
+class WebApp:
+    def __enter__(self):
+        print("🏁 Startup up!")
+        self.val = "Hello world"
+
+    @web_endpoint()
+    def web(self):
+        return {"message": self.val}