#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.noproxy.yaml

@@ -1,4 +1,4 @@
 services:
   frontend:
     ports:
-      - 8080:8080
+      - ${HTTP_PUBLISH_PORT:-8080}:8080