This PR introduces compile-time JSON parsing for C++26 users. Essentially, at compile time, you can load a JSON file (with embed) and parse... so if you JSON is like so...

{
  "name" : "John",
  "age": 5
 
}

Then calling our simdjson::compile_time::parse_json function, you get, at compile time... something like this pseudoC++:

struct {
  const char * name = "John";
  uint64_t age = 5;
}

It is a dynamically generated structure/class.

Thus you get the following...

constexpr auto cfg = simdjson::compile_time::parse_json<R"({
    "port": 8080,
    "host": "localhost",
    "debug": true
})">();

// cfg.port == 8080
// std::string_view(cfg.host) == "localhost"
// cfg.debug == true

We support JSON that take the form of an array or an object. We support full precision number parsing, and there is a bunch of validation (including Unicode checks), all at compile time. The strings are unescaped, including for Unicode data.

Joint work with @FranciscoThiesen and huge thanks to the C++26 reflection people.