Add Tooltip to Polygon Elements

[dansreis]

Description:
We would like to add a feature that allows tooltips to be displayed when hovering over polygon elements on the canvas. This enhancement will provide users with additional context or information about the polygon elements, improving the usability and interactivity of the react-canvas-annotator library.

Motivation:
Displaying tooltips on polygon elements can be highly beneficial for users who need to annotate images with additional information. Tooltips can provide immediate feedback and context without requiring users to click on the polygon elements, thereby improving the user experience.

Proposed Solution:

1. Introduce a new property for polygon elements to specify the tooltip content.
2. Update the rendering logic to display a tooltip when the user hovers over a polygon element.
3. Ensure the tooltip is styled appropriately and follows the cursor for better visibility.