Simplify configuration

Merged username-removed-124398 requested to merge NicoAlt/fdroid-website:gem-dependencies into master

With I was able to simplify the configuration needed for the plugin to work.

The only thing that needs to be added to _config.yml is the list with the two gems jekyll-paginate-v2 and jekyll-include-cache, also if I would like to remove that too:

CC @pserwylo