Implement a daily job to identify unknown ISO639-3 `Language` metadata value

[benoit74]

Once the CMS will have published the list of used ISO639-3 codes in any ZIM Language metadata with openzim/cms#102, libkiwix should regularly (daily?) check that it can properly recognize all these codes.

It is indeed libkiwix responsibility to provide a shared point of contact (API) for all readers regarding the meaning of every individual Language values. Should a value be unrecognized by libkiwix despite being value, we must quickly patch libkiwix so that corresponding ZIM are properly discoverable by all readers.

This issue comes from openzim/overview#51 (comment) discussion

[aviralgarg05]

I would like to solve this issue

[kelson42]

From the issue description, openzim/cms#102 ahould be implemented first.

[aviralgarg05]

From the issue description, openzim/cms#102 ahould be implemented first.

I will do that first then