Symfony command to reprocess all images to webp and reslugify image filenames

[jedi58]

Docker will need:

ADD https://raw.githubusercontent.com/mlocati/docker-php-extension-installer/master/install-php-extensions /usr/local/bin/
RUN chmod uga+x /usr/local/bin/install-php-extensions && sync && \
    install-php-extensions imagick

Also add imagick to RUN install-php-extensions \