Make local dev site port configurable

.env

@@ -0,0 +1 @@
+PORT=8080

docker-compose.yml

@@ -21,7 +21,7 @@ services:
   nginx:
     image: nginx:1.15
     ports:
-      - 8080:80
+      - ${PORT}:80
     volumes:
       - .:/usr/local/src/wellrested
       - ./docker/nginx/site.conf:/etc/nginx/conf.d/default.conf