Refactor Vue Zoomable Component & Scrolloverlay

[Robinrrr]

Description

These changes remove the extra Vue instance that is created in the VueZoomable component. There are also improvements in the ScrollOverlay component

Type of change

• Additional Vue Instance in VueZoomable.vue was removed. The ScrollOverlay was added in the component itself.
• Show the ScrollOverlay text only if wheelEnabled is true. It makes no sense to display the text if you have deactivated it
• Rename the enableWheelOnKey property to wheelKey for better understanding
• Re-Formatting some code