Upgrade base image from debian bullseye to bookworm, add pip and bulma

There was errors building netlify npm because node version was too old. Upgrading to bookworm fix the issue.

Add python3-pip as some building script needs to perform requirements install (Some python dependencies doesn't exist as Debian packages).

Add a part to clone Bulma, a css framework based on scss.

This will need further cleanup and optimisation in the future.