feat: 新增对象字面量和属性访问表达式

examples/input.ast

@@ -1,2 +1,2 @@
-let name = input("Your name: ");
-print("Hello, " + name)
+let name = io.input("Your name: ");
+io.print("Hello, " + name)

examples/object.ast

@@ -0,0 +1,4 @@
+let obj = { name: "aster", version: 1 }
+print(obj.name)
+obj.version = obj.version + 1
+print(obj.version)