Support multiple languages

[codesections]

tealdeer currently fetches all languages from the tldr.sh API. However, it only ever displays English documentation. It seems that tealdeer should offer a flag/config option that would display documentation from other languages, when available. (Or maybe it should read the $LANG environmental variable?)

Alternatively, if tealdeer is not going to display non-English documentation, it probably should not save the non-English docs in the user's cache (since they take up space without providing any benefit).

In an ideal world, tealdeer would offer a user the option of selecting their language(s) before downloading the cache, but that seems like a lower priority.

[dbrgn]

Yep, multilingual tldr pages are newer than tealdeer.

Would be nice to support all languages.

[dbrgn]

Actually, since tealdeer already supports the entire tldr pages repo, all languages will already be part of the cache (in $XDG_CACHE_HOME/tealdeer/tldr-master/).

What would be required:

• Add a config option to set the desired language
• If a page in that language exists, show it, otherwise fall back to the non-translated pages
• Add a command line argument (-L/--language) to override the language

[dbrgn]

Ah, there is a language resolution spec here: https://github.com/tldr-pages/tldr/blob/master/CLIENT-SPECIFICATION.md#language We should probably adhere to it.