Support other languages than english in search

[kmaasrud]

elasticlunr-rs provides support for different dictionaries to provide search functionality in other languages than english (see this). These dictionaries should not be included by default, as embedding them drastically increases the binary size. However, the user should get the option to include them if they so choose.

Consider adding this option in the next generation mdzk SSG.

Ref: See #68 (comment) from @huangziwei