Add test case for completion in the jsdoc type literals for typescript files.

tests/cases/fourslash/completionsAtJsDoc.ts

@@ -0,0 +1,8 @@
+/// <reference path="fourslash.ts" />
+
+////interface Foo<T> { }
+/////**
+//// * @type {Foo<{/**/}>}
+//// */
+
+verify.completions({ marker: "", exact: [], isNewIdentifierLocation: true });