Allow customization of "node_invalid_placement"

[Maryannah]

Describe the problem

Breaking HTML

<select name="accountType" required id="type-input" value={profile}>
        <!-- Here -->
	<button>
		<selectedcontent />
	</button>

	{#each profiles as p}
		<option value={p.value}>{p.label}</option>
	{/each}
</select>

This is now valid HTML as seen on MDN :
https://developer.mozilla.org/en-US/docs/Learn_web_development/Extensions/Forms/Customizable_select#customizable_select_markup

Describe the proposed solution

Have the ability to customize the rule AT YOUR OWN RISKS

I think it's delusional to think you can list all quirks of the language and protect users from them, so I prefer to ask for customization rather than adding rule after rule until you cover all use cases.

Importance

would make my life easier

[Prinzhorn]

See #15617

This is now valid HTML as seen on MDN :

whatwg/html#9799

I think it's delusional to think you can list all quirks of the language and protect users from them, so I prefer to ask for customization rather than adding rule after rule until you cover all use cases.

It's a compromise to help users prevent hard to debug bugs. If you insert invalid HTML, the browser will "fix it" leaving Svelte in an inconsistent state about what it thinks the DOM should look like.