Language-specific web content-discovery wordlists

**Describe the feature request**:
> Even though English is the most used language, some targets still use their own language in their application; for this reason, it's necessary to use wordlists adapted for this context.

The prospect of language-specific wordlists for things other than passwords seems interesting. But this might be difficult to develop without assistance from people that speak each language.

At least for web content-discovery, for every single line we should consider whether it comes from default filenames generated by software, or human-picked filenames. To generate each "final" language-specific wordlist we would combine the wordlist of default filenames with a wordlist of language-specific human-picked filenames, like we have done with the automatically-updating Discovery/Web-Content/combined_directories.txt wordlist.

We should also consider issue https://github.com/danielmiessler/SecLists/issues/1264. Also related, issue #1210

**Next steps**:
- [X] I intend to open a pull request later