Function to_lower_ascii

cpp/fory/util/string_util.h:204–206

constexpr bool is_digit_ascii(char c) { return c >= '0' && c <= '9'; }

constexpr char to_lower_ascii(char c) {
  return is_upper_ascii(c) ? static_cast<char>(c - 'A' + 'a') : c;
}

constexpr bool needs_snake_separator(std::string_view name, size_t index) {
  if (index == 0)