Readarr (Untested... should work...)

Requirements

Add 2 volumes to your container
/custom-services.d and /custom-cont-init.d (do not map to the same local folder...)
Docker Run Example:
-v /path/to/preferred/local/folder-01:/custom-services.d
-v /path/to/preferred/local/folder-02:/custom-cont-init.d
Download the script_init.bash and place it into the following folder: /custom-cont-init.d
Start your container and wait for the application to load
Optional: Customize the configuration by modifying the following file /config/extended.conf
Restart the container