Document and test std::ranges functionality

[lemire]

For C++20 users, we support std::ranges somewhat under the DOM API but it is undocumented.

#include "simdjson.h"
#include <iostream>
#include <ranges>
using namespace simdjson;
int main(void) {
  auto cars_json = R"( [
  { "make": "Toyota", "model": "Camry",  "year": 2018, "tire_pressure": [ 40.1, 39.9, 37.7, 40.4 ] },
  { "make": "Kia",    "model": "Soul",   "year": 2012, "tire_pressure": [ 30.1, 31.0, 28.6, 28.7 ] },
  { "make": "Toyota", "model": "Tercel", "year": 1999, "tire_pressure": [ 29.8, 30.0, 30.2, 30.5 ] }
] )"_padded;
  dom::parser parser;
  auto justmodel = [](auto car) { return car["model"]; };
  for (auto car : parser.parse(cars_json).get_array() | std::views::transform(justmodel)) {
    std::cout << car << std::endl;
  }
}

Also it would be nice to extend std::ranges to ondemand.