I have a repository that has multiple directories each containing a python script, a requirements.txt, and a Dockerfile. I want to use Github actions to build an image on merge to the main branch and push this image to Github packages. Each Dockerfile defines a running environment for the accompanying python script. But want to build only that directory's Dockerfile on which changes are made and tag each image with the directory name and a version number that is different from other directories version changes. How can I accomplish this? An example workflow.yml file would be awesome.