How can I attach an event when a certain class is added/removed to any tag?
<p>Let's suppose I have a css class named "foo".</p>

<p>I would like to have two event handlers:
- the first event handler would be triggered when "foo" is added as a class to any tag
- the second event handler would be triggered when "foo" is removed as a class from any tag</p>

<p>How can I achieve this?</p>

<p>Thank you in advance.</p>
