Update the URL for the pure javascript implementation, added a Dockerfile & fixed just a pure port not working

[axodouble]

This pull request is small, just wanted to use this for my own site but I deploy my things using docker.

While working on docker I noticed that a pure port doesn't work, (i.e ./comma /data 9991), so I added in a check for that.

I do believe though that this may benefit from maybe having a github actions workflow to automatically build and push the code to a container image on tagged releases? I have some working examples already but I do not want to push that on you without you being good with it.

Then I wanted to check your implementation for comments, but also noticed that the link is dead, just replaced with a prefixed underscore.

That should be all, let me know if this needs any changes.

[axodouble]

I have also created this tree on my own fork, if interested I can add this to the pull request but that changes the scope slightly, and will publish containers under the repo owners name.
So if you want to inspect the result, they are tagged under ghcr.io/axodouble/comma:latest