Using `Aside` directive in Markdown list context leads to invalid HTML

[agektmr]

Describe the bug
The articles that are using Details directive are broken.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://web.dev/security-headers/ or https://web.dev/strict-csp/
2. Scroll down to the bottom

Expected behavior
You can see the bottom of the page, but it's actually terminated at Details directive.

[jeffposnick]

This is due to a combination of the Markdown list parser and the {% Aside %} directive leading to invalid HTML output. The new HTML minifier we switched to in #7532 treats invalid HTML differently than the old minifier.

If you want to see the invalid HTML yourself, you can run npm run eleventy locally, then take, e.g., dist/security-headers/index.html and paste it into https://validator.w3.org/#validate_by_input. You'll see something like:

There are a few options for resolving this:

• We can get rid of the <li> elements created by the Markdown processor, by switching these from numbered items to <h4>s via ####:

web.dev/src/site/content/en/secure/security-headers/index.md

Line 355 in 244e5a0

1. Enforce Trusted Types for dangerous DOM sinks

• We can keep the numbered items, but don't use any {% Aside %} directives inside of them:

web.dev/src/site/content/en/secure/security-headers/index.md

Lines 379 to 385 in 244e5a0

	{% Aside %}
	You may limit allowed Trusted Types policy names by setting an additional
	`trusted-types` directive (for example, `trusted-types myPolicy`). However, this is
	not a requirement.
	{% endAside %}

• We can find out some way to massage the Markdown list parser + {% Aside %} output to produce valid HTML, but that will probably take longer.