refactor: reduce number of layers

[martabal]

Since this is a base image, we can reduce the number of layers to reduce the image size. The only side effect is that we can't use cache to speed up the build.

Added a crontab too in the github workflow so it builds the image automatically every 3 days.

[bo0tzz]

Thank you for tidying up the layers! I don't think we need the cron build, and we should discuss how exactly we want to build this anyways (ie whether it stays in this separate repo).

[martabal]

Thank you for tidying up the layers! I don't think we need the cron build, and we should discuss how exactly we want to build this anyways (ie whether it stays in this separate repo).

I removed the cron build 😃