Fallback server-side generated landing page and search for browsers without JavaScript

[ge0rg]

The "Welcome to Kiwix Server" landing page and wiki search on the / URL requires JavaScript to query the API for a list of matching books and to render the results.

While I appreciate the individual books popping up in a shiny animation, the result list is always empty on devices that do not support JavaScript, like older ebook readers which are a relevant target for offline reading of ZIMs.

This is also a regression in comparison to 2.1.0.

Actual result:

Anticipated result:

[kelson42]

Duplicate of #615