Function is_boolean

Source/external/json.hpp:20487–20490

@brief return whether value is a boolean @sa https://json.nlohmann.me/api/basic_json/is_boolean/

	/// @brief return whether value is a boolean
	/// @sa https://json.nlohmann.me/api/basic_json/is_boolean/
	constexpr bool is_boolean() const noexcept
	{
		return m_type == value_t::boolean;
	}

	/// @brief return whether value is a number
	/// @sa https://json.nlohmann.me/api/basic_json/is_number/