Function is_utf8_continuation

include/engine/framework/text/utf8.h:10–12

namespace engine::text {

inline bool is_utf8_continuation(unsigned char ch) noexcept {
    return (ch & 0xC0U) == 0x80U;
}

inline size_t utf8_codepoint_count(std::string_view text, std::string_view label) {
    size_t count = 0;