ui: Initial Elm UI import

Merged from https://github.com/jhillyerd/inbucket-elm

Uses https://github.com/halfzebra/create-elm-app

ui/public/manifest.json

@@ -0,0 +1,15 @@
+{
+  "short_name": "Elm App",
+  "name": "Create Elm App Sample",
+  "icons": [
+    {
+      "src": "favicon.ico",
+      "sizes": "192x192",
+      "type": "image/png"
+    }
+  ],
+  "start_url": "./index.html",
+  "display": "standalone",
+  "theme_color": "#000000",
+  "background_color": "#ffffff"
+}