Show text on hover

I currently have a custom HTML element inside my markdown. Example below:

I want to create a popup that shows when you hover over the HTML that shows the data stored in the tag

I’m not even sure where to start looking in terms of documentation… Anyone able to point me in the right direction?

<mark data="I want this text to show on hover"> This text is highlighted </mark>

This thread might give you some ideas:

Using the aria-label attribute might work.