Multi-language build example

[Osamu Aoki]

Hi,

I am converting Debian Developers Reference to Sphinx.
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=931548

I have created document source tree with multiple languages.
https://salsa.debian.org/debian/developers-reference/tree/rest8

I can now build all HTML files for all languages just by "make". But
the generated HTML page lacks "language_switcher_placeholder" (*) which
is available for site like https://docs.python.org/3/ to jump between
translations.

(*) <span class="language_switcher_placeholder"><select><option value="en" selected="selected">English</option><option value="fr">French</option><option value="ja">Japanese</option><option value="ko">Korean</option><option value="zh-cn">Simplified Chinese</option></select></span>

Is there any good example source tree which shows me "BEST PRACTICE" to
achieve multi-language build results in-line with
https://docs.python.org/3/ which has language selection pull down
selector.

Osamu