devtools/hackdoc: serve JS with correct mimetype

This allows us to serve rich content from hackdoc, eg. hbj11's
webflaser.

Change-Id: Ife83888d864db0b2eddf3a50b0129be0172aad8a
diff --git a/devtools/kube/hackdoc.libsonnet b/devtools/kube/hackdoc.libsonnet
index 93b01bc..4fd7ad6 100644
--- a/devtools/kube/hackdoc.libsonnet
+++ b/devtools/kube/hackdoc.libsonnet
@@ -3,7 +3,7 @@
 
 {
     cfg:: {
-        image: "registry.k0.hswaw.net/q3k/hackdoc:315532800-a415ced850425a195f96b331f57cd78f15e622d9",
+        image: "registry.k0.hswaw.net/q3k/hackdoc:315532800-f4d02581f60b18a8635d026079ed67039cdc45e6",
         publicFQDN: error "public FQDN must be set",
     },