add a minimal readme for the haproxy image

images/haproxy/README.md

@@ -0,0 +1,14 @@
+# haproxy
+
+This image is used internally by kind to implement kubeadm's "HA" mode,
+specifically to load balance the API server.
+
+We cannot merely use the upstream haproxy image as haproxy will exit without
+a minimal config, so we introduce one that will list on the intended port and
+hot reload it at runtime with the actual desired config.
+
+## Building
+
+You can `docker build -t kindest/haproxy .` in this directory to build a test image.
+
+To push an actual image use `./push-cross.sh`.