How do I make a case-insensitive attribute filter with uBlock Origin?

I want to create a case-insensitive cosmetic filter in uBlock Origin that matches elements based on attribute value.

For example, let’s say a page had the following elements.

<a href="/advertisement">
<a href="/ADVERTISEMENT">
<a href="/AdVeRtiSeMeNt">

When I write a cometic filter, it will only match if the capitalization is the same.

example.com##[href="/advertisement"]

How can I write a case-insensitive uBlock filter that matches an attribute value regardless of capitalization?