Added checks to make sure the specified track exists

Added precondition checks to validate input files and paths to return more informative error messages as per #2

node_modules/jest-leak-detector/build/index.d.ts

@@ -0,0 +1,14 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+export default class {
+    private _isReferenceBeingHeld;
+    constructor(value: unknown);
+    isLeaking(): boolean;
+    private _runGarbageCollector;
+    private _isPrimitive;
+}
+//# sourceMappingURL=index.d.ts.map