Review extensions installation guidance

ckan/Dockerfile

@@ -1,5 +1,7 @@
 FROM ckan/ckan-base:2.10.1
 
+# Install any extensions needed by your CKAN instance
+# See Dockerfile.dev for more details and examples
 
 # Copy custom initialization scripts
 COPY docker-entrypoint.d/* /docker-entrypoint.d/

ckan/Dockerfile.dev

@@ -1,16 +1,13 @@
 FROM ckan/ckan-dev:2.10.1
 
-
-# Set up environment variables
-ENV APP_DIR=/srv/app
-
 # Install any extensions needed by your CKAN instance
 # - Make sure to add the plugins to CKAN__PLUGINS in the .env file
-# - Also make sure all extra configuration options are added to the CKAN config file (ckan.ini)
-#   This can be done by creating an overriding start_ckan_dev_development.sh file:
-#   (https://github.com/ckan/ckan-docker-base/blob/main/ckan-2.9/dev/setup/start_ckan_development.sh) ie: updating the 'ckan config-tool' lines
-#   For more on config-tool please see https://docs.ckan.org/en/latest/maintaining/cli.html#config-tool-tool-for-editing-options-in-a-ckan-config-file
-#   or using Crudini (https://github.com/pixelb/crudini) 
+# - Also make sure all provide all extra configuration options, either by:
+#   * Adding them to the .env file (check the ckanext-envvars syntax for env vars), or
+#   * Adding extra configuration scripts to /docker-entrypoint.d folder) to update
+#      the CKAN config file (ckan.ini) with the `ckan config-tool` command
+#
+# See README > Extending the base images for more details
 #
 # For instance:
 #