JS: Add type-tracking test

Author: asgerf

javascript/ql/test/library-tests/TypeTracking/TypeTracking.expected

@@ -0,0 +1,2 @@
+| summarize.js:30:14:30:26 | // track: obj | Failed to track obj here. |
+| summarize.js:33:14:33:26 | // track: obj | Failed to track obj here. |

javascript/ql/test/library-tests/TypeTracking/summarize.js

@@ -0,0 +1,33 @@
+import 'dummy';
+
+function identity(x) {
+    return x;
+}
+function load(x) {
+    return x.loadProp;
+}
+function store(x) {
+    return { storeProp: x };
+}
+function loadStore(x) {
+    return { storeProp: x.loadProp };
+}
+
+identity({});
+load({});
+store({});
+loadStore({});
+
+const obj = {}; // name: obj
+
+let x = identity(obj);
+x; // track: obj
+
+x = load({ loadProp: obj });
+x; // track: obj
+
+x = store(obj);
+x.storeProp; // track: obj
+
+x = loadStore({ loadProp: obj });
+x.storeProp; // track: obj