Fix a few invalid HTML elements generated by javascript

[rdwebdesign]

What does this PR aim to accomplish?

Fix invalid HTML code.

This code is generating an invalid HTML (lists cannot be inside a <p> tag):

web/scripts/pi-hole/js/settings-advanced.js

Lines 14 to 20 in 4ed958d

	"<p>Available options: <ul><li>" +
	allowed
	.map(function (option) {
	return "<code>" + option.item + "</code>: " + utils.escapeHtml(option.description);
	})
	.join("</li><li>") +
	"</li></ul></p>"

The expected code would be:

<p>Available options:
  <ul>
    <li>...</li>
  </ul>
</p>

But this is invalid. Most browser parsers will try to fix it and the final HTML code will be:

<p>Available options:</p>   <--- paragraph implicitly closed
<ul>
  <li>...</li>
</ul>
<p></p>   <--- Empty paragraph created

Also, we insert the generated code inside another <p> element.

This is currently doing nothing (the empty paragraph just creates a small extra line in some cases), but if we add more elements to the functions, the generated code could break the layout.

How does this PR accomplish the above?

Fixing the javascript generating HTML and replacing a few <p> tags by <div> tags (A <div> element can be parent of <p> and <ul> elements).

Reference:

A p element's end tag can be omitted if the p element is immediately followed by an (...), ol, p, (...), or ul element ...

Details explaining this behavior can be found on the last Note of the 4.4.1 section:

• https://html.spec.whatwg.org/multipage/grouping-content.html#the-p-element:the-ul-element-2

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