Function convert_hex_to_binary

src/unicode.cpp:448–450

    12, 13, 14, 15, 0, 0, 0, 0, 0, 0, 0, 0,  0,  0,  0,  0,  0, 0,  0,
    0,  0,  0,  0,  0, 0, 0, 0, 0, 0, 0, 10, 11, 12, 13, 14, 15};
unsigned constexpr convert_hex_to_binary(const char c) noexcept {
  return hex_to_binary_table[c - '0'];
}

std::string percent_decode(const std::string_view input, size_t first_percent) {
  // next line is for safety only, we expect users to avoid calling