Fix No results with direct Libgen fallback.
Adds direct Libgen fallback when Anna is gone.
Since the DDoS guard seems to stay with us for a while the plugin will now directly search Libgen for queries. While the original implementation would look for results from different hosts, most files should be available on Libgen as well.
Note that search filters might not work as well as on Annas.
Also added Czech and Slovak language filters.