feat: add Std::Json — JSON parser and serializer

- JsonValue struct supporting null, bool, number, string, array, object
- Json_Parse(s: String) -> JsonValue: recursive descent parser
- Json_Stringify(v: JsonValue) -> String: recursive serializer
- Access helpers: Json_ObjectGet, Json_ObjectSet, Json_ObjectHas,
  Json_ArrayGet, Json_ArrayPush, Json_ArrayLen, Json_ObjectLen
- Constructors: Json_Null, Json_Bool, Json_Number, Json_String,
  Json_Array, Json_Object
- Type accessors: Json_IsNull, Json_AsBool, Json_AsNumber, Json_AsString
- examples/json.bux: demonstrates parse, access, build programmatically
- Add os_time, process, json to test-examples suite

_test_json_arr2/bux.toml

@@ -0,0 +1 @@
+[Package]

_test_json_arr2/src/Main.bux

@@ -0,0 +1,17 @@
+import Std::Io::{PrintLine};
+
+struct JsonValue {
+    tag: int,
+    strVal: String,
+    numVal: float64
+}
+
+extern func bux_alloc(size: uint) -> *void;
+
+func Main() -> int {
+    let cap: uint = 4;
+    let data: *JsonValue = bux_alloc(cap * sizeof(JsonValue)) as *JsonValue;
+    data[0] = JsonValue { tag: 1, strVal: "first", numVal: 1.0 };
+    PrintLine(data[0].strVal);
+    return 0;
+}