Templates should all contain valid HTML, if any, as it is expected to be parsed as part of rendering.
This rule disallows invalid HTML in templates.
The following patterns are considered warnings:
html`<x-foo />`;
html`<x-foo invalid"attribute></x-foo>`;
The following patterns are not warnings:
html`<x-foo bar=${true}></x-foo>`;
If you don't care about invalid HTML, then you will not need this rule.