This tutorial describes a way to redefine the <mark> and <slot> tags to highlight text parts.
Since creating this video I have realised that <slot> cannot have any block-level attributes, so due to that I probably wouldn’t use it.
Please just focus on using <mark> tags
A <mark> tag by default places a light yellow background behind the enclosed contents. We will create CSS classes to change this behaviour. This can be very effective for changing the colour is a text part, underlining it or putting a block color behind it.