Document better why we use hostPort on node-exporter

Signed-off-by: ArthurSens <arthursens2005@gmail.com>

jsonnet/kube-prometheus/components/node-exporter.libsonnet

@@ -201,6 +201,12 @@ function(params) {
       // used by the service is tied to the proxy container. We *could*
       // forgo declaring the host port, however it is important to declare
       // it so that the scheduler can decide if the pod is schedulable.
+      //
+      // Although hostPort might not seem necessary, kubernetes adds it anyway
+      // when running with 'hostNetwork'. We might as well make sure it works
+      // the way we want.
+      //
+      // See also: https://github.com/kubernetes/kubernetes/blob/1945829906546caf867992669a0bfa588edf8be6/pkg/apis/core/v1/defaults.go#L402-L411
       ports: [
         { name: 'https', containerPort: ne._config.port, hostPort: ne._config.port },
       ],