Hello,

Thanks for your hard work. I'm having issues adding custom tags or custom attributes to the editor. I'm loading the Trix editor with initial value `Hello Trix!` (via an attached `` tag) but the Trix editor's input displays `

` once the library loads.

Here is a minimal project that reproduces the issue:

```HTML

document.addEventListener("trix-before-initialize", function() {
console.log("Trix is about to initialize!");

// According to the README.md, this should add support for custom tags and attributes
Trix.config.dompurify.ADD_TAGS = [ 'my-custom-tag' ]
Trix.config.dompurify.ADD_ATTR = [ 'id' ];
});

Welcome to My Website

This is a simple HTML page.

```

Note that the editor's input displays `

`. I would expect the editor's input to display my original HTML value.

Am I setting up the project incorrectly? I skimmed through the code and it seemed to me that the config that we pass to `Trix.config.dompurify` is not being used when parsing HTML.

Thank you for reviewing this ticket.

Start with the minimal HTML reproduction and the trix-before-initialize handler, then trace how Trix.config.dompurify is applied while the input value is parsed. Verify whether the configured custom tag and id attribute survive initialization; done means the editor preserves the supplied custom HTML rather than displaying a div-only version.

Written by the indexing model from the issue text.