chore: document USER_ID and GROUP_ID in docker-compose.yml

Author: kwvg

contrib/containers/develop/docker-compose.yml

@@ -4,6 +4,9 @@ services:
     build:
       context: '..'
       dockerfile: './develop/Dockerfile'
+      args:
+        USER_ID: 1000   # set this to $(id -u) of the host
+        GROUP_ID: 1000  # set this to $(id -g) of the host
     ports:
       - "9998:9998"           # Mainnet Ports
       - "9999:9999"