comp review todo app update (#146)

* new todo frontend

* yarn --> npm

* basic Dockerfile

* add Helm chart for todo list

* backend working

* connect new-app'd frontend to backend via proxy_pass

* move nginx conf

* move nginx conf back

* move helm chart to course repo

* add simple SSR node.js service

* log error message

* fix host typo

* fix dockerfiles

* add link to items page

* improve probe route for todo-backend

* canary probe route for todo-backend

* Dockerfile -> Containerfile todo-backend

* Dockerfile -> Containerfile todo-frontend

* remove commands for containerfile as part of comp review

todo-ssr/views/index.pug

@@ -0,0 +1,6 @@
+html
+  head
+    title= title
+  body
+    h1= message
+    a(href="/items") To Do List

todo-ssr/views/items.pug

@@ -0,0 +1,11 @@
+html
+  head
+    title Todo Items
+  body
+    h1 Todo List
+    p Note that this version is non-interactive
+    ul
+      each item in items
+        li
+          input(type="checkbox" disabled="disabled" checked=item.done ? "checked" : "")
+          span= item.description