Optionally use Contour in hack/prepare-supervisor-on-kind.sh

Using Contour for ingress allows us to avoid using the hacky proxy
server approach. This makes it easy to use any web browser to complete
the login process, since there is no need to configure the proxy server
for the browser.

hack/lib/kind-config/contour-overlay.yaml

@@ -0,0 +1,16 @@
+#! Copyright 2023 the Pinniped contributors. All Rights Reserved.
+#! SPDX-License-Identifier: Apache-2.0
+
+#@ load("@ytt:overlay", "overlay")
+#@overlay/match by=overlay.subset({"kind": "Cluster"}), expects=1
+---
+#! Appends another port mapping to every node in the CLuster config.
+#! Contour will use this port mapping to expose the https endpoints
+#! of in-cluster apps at localhost:443 on your host.
+nodes:
+  #@overlay/match by=overlay.all, expects="1+"
+  - extraPortMappings:
+      - protocol: TCP
+        containerPort: 443
+        hostPort: 443
+        listenAddress: 127.0.0.1