devel/libkiwix: Update 12.1.0 → 13.1.0

Selected list of improvements:

• C++17 compatible code
• Improved look & feel of kiwix-serve UI
• Increase tolerance to malformed (control characters) ZIM entry titles
• API allowing to filter many categories at once
• Cookie-less user language control
• Properly translated error pages
• Properly translated search result page
• Default UI language is resolved in frontend
• Better support of older Web browsers by polyfilling replaceAll()
• New API to migrate bookmarks between books

See also:
https://github.com/kiwix/libkiwix/releases/tag/13.0.0
https://github.com/kiwix/libkiwix/releases/tag/13.1.0

This is a maintainer update (olce.freebsd.ports@certner.fr).

Approved by: jrm (ports)
Approved by: emaste (mentor)