Hi, thanks for reporting ??
In fact the script does work but there is a HTML5 opacity detection failing which means search terms are now wrapped in SPAN tags instead of HTML5 MARK tags. Now, the browser does not apply the default marker background color anymore.
This will be fixed in the upcoming release but in the mean time, please add the simple CSS rule to your Appearance > Customizer > Custom CSS:
.hilite {
background-color: yellow;
}
(replace the background color with any other if you want it to match your theme better)
Let me know if this works for you ??