#1402 Environment variables for custom image (#1403)

* chore: enhance compose.yaml with variables for customize

* chore: use default blank values for db and redis variables in compose.yaml

* chore: Use env var for HTTP(S) publish ports in overrides

* docs: explain use of environment variables for image customization

* chore: use ERPNEXT_VERSION as default

* docs: fixed spelling errors

overrides/compose.traefik.yaml

@@ -35,7 +35,7 @@ services:
       # Enable the Dashboard and API
       - --api
     ports:
-      - 80:80
+      - ${HTTP_PUBLISH_PORT:-80}:80
     volumes:
       - /var/run/docker.sock:/var/run/docker.sock:ro
     networks: