nginx-golang: add dev envs support (#273)

* Add Docker Desktop Developer Environments config
* Upgrade from Go 1.13 (🙀) to 1.18
* Rename `frontend` -> `proxy` for clarity & consistency
  with other samples
* Add Chi as a dependency to provide an example of Go
  module dependencies for parity with other samples

Signed-off-by: Milas Bowman <milas.bowman@docker.com>

nginx-golang/compose.yaml

@@ -1,9 +1,17 @@
 services:
-  frontend:
-    build: frontend
+  proxy:
+    image: nginx
+    volumes:
+      - type: bind
+        source: ./proxy/nginx.conf
+        target: /etc/nginx/conf.d/default.conf
+        read_only: true
     ports:
       - 80:80
     depends_on:
       - backend
+
   backend:
-    build: backend
+    build:
+      context: backend
+      target: builder