Add Codespaces configuration and make it the default

[0-vortex]

Having early access to GitHub Codespaces is really nice but the default containers could use some docker layer optimisation and push to the existing 0vortex/dotfiles tag as latest or codespaces.

Some additional configuration is required to make GitHub pull this ready-to-go image in every code space and some dotbot codification to make it potentially skip the configuration entirely in devcontainers.