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/proxy/nginx.conf

@@ -0,0 +1,6 @@
+server {
+  listen 80;
+  location / {
+    proxy_pass http://backend:80;
+  }
+}