* [DURACOM-303] prevent possibly long-lasting search and browse calls in SSR
* [DURACOM-303] implement skeleton component for search results
* [DURACOM-303] add skeleton loader for search results and filters
* [DURACOM-303] minor restyle of skeleton for mobile
* [DURACOM-303] fix lint and tests
* [DURACOM-303] adapt tests
* [DURACOM-303] restyle skeleton, add filter badge skeleton
* [DURACOM-303] add loop for filters count
* [DURACOM-303] add grid layout, make SSR enabling configurable, minor restyle of skeletons
* [DURACOM-303] refactor param, add example of configuration
* [DURACOM-303] rename variable, minor code refactor
* [DURACOM-303] add override possibility with input
* [DURACOM-303] fix SSR check on template and on components missing the environment config. Add descriptive comment for skeleton component. Fix JS error on SSR.
* [DURACOM-303] refactor thumbnail's skeleton style
Because Angular SSR is not very efficient, after discussion with
the Google Scholar team we realized a compromise would be to only
use SSR for pages in the DSpace sitemap (and the home page).
