Support à la carte dependencies

scraperlib grew significantly over the years, with modules very useful even beyond pure scraper usages. The ZIM wrapper is very useful in itself to name only one.

We are also considering addition of the currently separate kiwixstorage module, or the Kiwix catalog reader.

To support this Kiwix Swiss-army knife layout, we'd need to be able to install only some of the dependencies.

Dependencies would thus be organized into extra groups (ZIM, image, video, etc) with an all group that installs everything of course.

In addition, we could maybe had a try block on imports in each module to print a user-actionable message when importing code for which dependencies are not installed.

Comienza revisando la configuración de dependencias del proyecto y las importaciones de módulos mencionadas en la issue. Define cómo deben organizarse los extras de ZIM, imagen y vídeo, incluido el grupo all, y determina si los mensajes de dependencias faltantes están dentro del alcance. Se considera completado cuando los extras seleccionados se pueden instalar de forma independiente y el comportamiento de importación acordado está cubierto.