Warns that attributes were duplicated in one element. Capital letters and lower case letters are not distinguished.
There must never be two or more attributes on the same start tag whose names are an ASCII case-insensitive match for each other. [cite: https://html.spec.whatwg.org/#attributes-2]
👎 Examples of incorrect code for this rule
<div data-attr="value" data-Attr="db"></div>
👍 Examples of correct code for this rule
<div data-attr="value" data-Attr2="db"></div>