Simplify install documentation

[k1o0]

Currently the documentation informs users to clone Alyx then deploy containers that also contain Alyx. This is confusing and necessary. Instead users can deploy with just the compose file, perhaps after downloading via curl.

Some proposed changes:

• For production, users can download the compose file alone
• A requirements section should specify the minimum production OS version and drive space
• Instructions for poking around can instruct the user to clone the repo and compose the postgres container
• Document the release process in the contributing section of the readme

[oliche]

So in the end, we will document 2 installations:

1. fully containerized deployment
2. editable install with postgres container backend

[Sanjeev-Narang]

@k1o0 We can implement a CD workflow to publish pre-built images to GHCR. This removes the need for cloning the repo and local building the docker image. I would really appreciated it if you could assign this to me.

[oliche]

Yes, we have done this as part of release 3.6.0, #954, although we are using dockerhub, and not github container registry !