Web internationalization

[mukrop]

Originally, the website https://logic.robotirckytabor.cz was set up quite in a hurry. Now, I think it's worth thinking about whether (and potentially how) it should handle internationalization. Many Logics distributed via Red Hat will have non-Czech speaking recipients, but Logics distributed by other means (we'll be sending a bunch to a programming class in Prague, potentially those distributed via Instruktori Brno) may benefit from Czech materials (which actually already exist at https://2021.robotickytabor.cz/logic/). Furthermore, updating two places will be complicated. This issue was seen already at the point of setting up the English website but was deliberately postponed due to the lack of time.

Thus:

1. Decide what language mutations will be maintained (both EN and CZ make sense to me).
2. Decide on the implementation of the above.
3. If other places remain (e.g. I expect the page of the 2021 camp will probably not be changed), they may benefit from a banner pointing to a maintained place.

[JakubAndrysek]

Localize the home page and prepare for the future localization: 100d09c