Optional Mount Parameters (#123)

* adding optional parameters

* updating bodyText mount prop to default

* updating snapshot for new props

* adding parent element for mounting

* adding null default for parentElement

* adding dist to gitignore

* adding test case for mounting to element

* adding div to document in test

* unmount after test

* updating test to pass

* updating eslint to handle certain rules as warning and fix others

public/blank.html

@@ -8,7 +8,9 @@
     
     <script src="./widget.js"></script>
     <script>
-      EmbeddableWidget.mount();
+      EmbeddableWidget.mount({
+        bodyText: 'Body'
+      });
     </script>
   </body>
 </html>