RFC: Replace the Docker-based development by using Composer and Drush directly.

For this to work, we need to install the following packages in the development VM

php-opcache php-apcu php-pdo php-sqlite3 php-dom php-xml php-zip php-gd composer zip sqlite3 node-node-sass

as proposed in the companion MR umwelt-info/infrastruktur/entwicklung!70 (merged).

Closes #12 (closed)

Closes #14 (closed)