Support for Custom Dockerfiles using the Docker Executor

Apologies if this is already supported but I didn't see it in the docs. Currently in the docs it says you can either supply an image name or existing container name to use with the docker executor: https://docs.dagu.cloud/features/executors/docker#configuration-reference-step-level

> Notes:
>
> * Set image, containerName, or both. If both are omitted, the step fails validation.
> * With only containerName, the target container must already be running; Dagu will exec into it using the exec options.
> * With both image and containerName, Dagu first attempts to exec into the named container. If it is missing or stopped, Dagu creates it using the supplied image (applying container/host/network settings) before running the command.

However I would like to use a local Dockerfile instead of using an official image or custom registry. Is it possible for me to point the Docker executor at a local dockerfile to use?