add(server.tests.test2): 添加实验2的内容，将pdf里面标重要的进行提取出来

Server/tests/test2/important/unshift.js

@@ -0,0 +1,12 @@
+// let len = array.unshift(element1, ..., elementN);
+
+const animals = ["pigs"]
+let rst = animals.unshift("dogs", "cats")
+console.log(rst)
+console.log(animals)
+
+/*
+# node unshift.js 
+3
+[ 'dogs', 'cats', 'pigs' ]
+*/