Better default for DOCKER_USER

This default value will make docker build image to work without worrying about user permissions.

readthedocs/settings/dev.py

@@ -51,6 +51,10 @@ def DATABASES(self):  # noqa
     # Disable auto syncing elasticsearch documents in development
     ELASTICSEARCH_DSL_AUTOSYNC = False
 
+    # UID and GID used to create the Docker container. It defaults to the
+    # current UID and GID that it's running the Django app.
+    DOCKER_USER = f'{os.geteuid()}:{os.getegid()}'
+
     @property
     def LOGGING(self):  # noqa - avoid pep8 N802
         logging = super().LOGGING