Add jsoncons lib (#130)

* Add jsoncons

* Fix the added version

* Including directly the include folder

packages/j/jsoncons/xmake.lua

@@ -0,0 +1,51 @@
+package("jsoncons")
+
+    set_homepage("https://danielaparker.github.io/jsoncons/")
+    set_description("A C++, header-only library for constructing JSON and JSON-like data formats, with JSON Pointer, JSON Patch, JSONPath, JMESPath, CSV, MessagePack, CBOR, BSON, UBJSON")
+
+    set_urls("https://github.com/danielaparker/jsoncons/archive/$(version).zip",
+             "https://github.com/danielaparker/jsoncons.git")
+
+    add_versions("v0.158.0", "7ad7cc0e9c74df495dd16b818758ec2e2a5b7fef8f1852841087fd5e8bb6a6cb")
+
+    on_install(function (package)
+        os.cp("include", package:installdir())
+    end)
+
+    on_test(function (package)
+        assert(package:check_cxxsnippets({test = [[
+            #include <iostream>
+            #include <string>
+            using namespace jsoncons;
+            std::string data = R"(
+                            {
+                                "application": "hiking",
+                                "reputons":
+                                [
+                                    {
+                                        "rater": "HikingAsylum",
+                                        "assertion": "advanced",
+                                        "rated": "Marilyn C",
+                                        "rating": 0.90,
+                                        "generated": 1514862245
+                                    }
+                                ]
+                            }
+                        )";
+            void test() {
+                json j = json::parse(data);
+                std::cout << "(1) " << std::boolalpha << j.contains("reputons") << "\n\n";
+                const json &v = j["reputons"];
+                for (const auto &item : v.array_range()) {
+                    // Access rated as string and rating as double
+                    std::cout << item["rated"].as<std::string>() << ", "
+                            << item["rating"].as<double>() << "\n";
+                }
+                std::cout << "\n";
+                std::cout << "(3)\n";
+                json result = jsonpath::json_query(j, "$..rated");
+                std::cout << pretty_print(result) << "\n\n";
+                std::cout << "(4)\n" << pretty_print(j) << "\n\n";
+            }
+        ]]}, {configs = {languages = "c++11"}, includes = {"jsoncons/json.hpp", "jsoncons_ext/jsonpath/jsonpath.hpp"}}))
+    end)