New port: databases/sqliteconvert

Sqliteconvert is a set of tools to convert SQLite3 schema files into
documentation. It includes sqlite2dot(1), which converts into a
graphviz file; sqlite2html(1), which converts into an HTML5 fragment;
and sqliteconvert(1), which pulls these tools together with some sane
default templates.

WWW: https://kristaps.bsd.lv/sqliteconvert/

Approved by: lme (mentor)
Differential Revision: https://reviews.freebsd.org/D9895