Method parse

tests/autotester/json11.hpp:158–167

                      std::string & err,
                      JsonParse strategy = JsonParse::STANDARD);
    static Json parse(const char * in,
                      std::string & err,
                      JsonParse strategy = JsonParse::STANDARD) {
        if (in) {
            return parse(std::string(in), err, strategy);
        } else {
            err = "null input";
            return nullptr;
        }
    }
    // Parse multiple objects, concatenated or separated by whitespace
    static std::vector<Json> parse_multi(
        const std::string & in,