libgrapheme is an extremely simple freestanding C99 library providing
utilities for properly handling strings according to the latest Unicode
standard 15.0.0.  It offers fully Unicode compliant grapheme cluster
(i.e. user-perceived character) segmentation, word segmentation,
sentence segmentation, detection of permissible line break
opportunities, case detection (lower-, upper- and title-case) and case
conversion (to lower-, upper- and title-case) on UTF-8 strings and
codepoint arrays, which both can also be null-terminated.