I don’t know if you’ve come across this but Chrome has a build in developer console which will show you the CSS, etc.
It’s not on hover, but if you right-click on the HTML element you’re interested in and select inspect element it’ll give you the CSS and the markup, etc.
This is built in, open Chrome, press F12, make sure you are on the Elements section (top toolbar), then click the magnifying glass in the status bar, hover over any element you want to look at closer.