move all vlib modules to vlib/

vlib/json/json_test.v

@@ -0,0 +1,21 @@
+import json 
+
+struct User {
+	age  int
+	nums []int
+}
+
+fn test_parse_user() {
+	s := '{"age": 10, "nums": [1,2,3]}'
+	u := json.decode(User, s) or {
+		exit(1) 
+		return
+	}
+	assert u.age == 10
+	assert u.nums.len == 3
+	assert u.nums[0] == 1 
+	assert u.nums[1] == 2 
+	assert u.nums[2] == 3 
+}
+
+