Split development config from production config

in `docker-compose.yml` and `docker-compose.override.yml`. This should speed
up builds e.g. on Travis CI, which does not need to sync folders or run
`yarn run dev` if the docker image was built recently. Also it should
make the build more reliable as it behaves more similar to our deployment.

docker-compose.override.yml

@@ -0,0 +1,11 @@
+version: '3.7'
+
+services:
+  webapp:
+    volumes:
+      - .:/HC-WebApp
+      - node_modules:/HC-WebApp/node_modules
+    command: yarn run dev
+
+volumes:
+  node_modules:

docker-compose.yml

@@ -2,17 +2,13 @@ version: '3.7'
 
 services:
   webapp:
-    build:
-      context: .
+    image: humanconnection/nitro-web:latest
+    build: .
     ports:
       - 3000:3000
       - 8080:8080
     networks:
       - hc-network
-    volumes:
-      - .:/HC-WebApp
-      - node_modules:/HC-WebApp/node_modules
-    command: yarn run dev
     environment:
       - HOST=0.0.0.0
       - BACKEND_URL=http://backend:4000