fix: Hover state background to be solid

[pdenya]

Summary

In latest Chromium browsers the HoverMsg element is displayed underneath the drag text and the opacity is too low to be readable.

(mouse circle from screen recording software)

Key Changes

• Updated Opacity from .5 to .9
• Added z-index on HoverMsg style

Updated look

(mouse circle from screen recording software)

Check List

• [x] The changes to the "Readme" file(if needed)
• [x] The changes not breaking any old rule of the library or usage

[KarimMokhtar]

Hi @pdenya , Thank you so much for your contribution. Could you please just follow the PR semantic rules to pass the checks?