add quickinfo test

Author: ajafff

tests/cases/fourslash/quickInfoForDestructuringShorthandInitializer.ts

@@ -0,0 +1,7 @@
+/// <reference path='fourslash.ts' />
+
+////let a = '';
+////let b: string;
+////({b = /**/a} = {b: 'b'});
+
+verify.quickInfoAt("", "let a: string");