ACR purge based on number of containers

I have a need to define a number of containers to keep rather than purging based on age. I found https://docs.microsoft.com/en-us/azure/container-registry/container-registry-auto-purge about creating a task but it only seems to support removal by age. Searching further I found a https://github.com/goyalmohit/acr-cleanup which would do the job but I was wondering what the best way to implement this might be. I don't want to spin up a VM just for this job to execute so I considered a container scheduled to start, run the script, and then stop. But is there anyway I can create some sort of scheduled task within Azure itself to run this?