feat(users/Profpatsch): init HtmxExperiment

I’m playing around with htmx (server-side html snippet rendering),
this is a simple registration form and some form validation that
happens in-place.

Change-Id: I29602a7881e66c3e4d1cc0ba8027f98e0bd3461c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8660
Tested-by: BuildkiteCI
Reviewed-by: Profpatsch <mail@profpatsch.de>
Autosubmit: Profpatsch <mail@profpatsch.de>

users/Profpatsch/hie.yaml

@@ -0,0 +1,11 @@
+cradle:
+  cabal:
+    - path: "./my-prelude"
+      component: "lib:my-prelude"
+    - path: "./htmx-experiment/src"
+      component: "lib:htmx-experiment"
+    - path: "./htmx-experiment/src"
+      component: "lib:htmx-experiment"
+    - path: "./htmx-experiment/Main.hs"
+      component: "htmx-experiment:exe:htmx-experiment"
+