Add test for format on key

tests/cases/fourslash/server/formatonkey.ts

@@ -0,0 +1,12 @@
+/// <reference path='fourslash.ts' />
+
+////switch (1) {
+////    case 1:
+////        {
+////            /*1*/
+////        break;
+////}
+
+goTo.marker("1");
+edit.insert("}");
+verify.currentLineContentIs("        }");