How to index pages on external site

The site I work on uses Docusaurus. I am an Algolia n00b!

This is the existing algolia.config.json:

This is the site:

I’ve heard that Algolia can index content on sites outside of the site where my algolia.config.json lives.

I want to be able to show search results that include the content on this external site page and its child pages:

Because I want it to index not just this page, but all of its child pages, I think this would be expressed as*

To do this, can I just add something like this to the start_urls section of my algolia.config.json?

    "url": "*",
    "tags": "flutter-sdk-reference",
    "selectors_key": "flutter-sdk-reference"

And something like this to the selectors section?

  "flutter-sdk-reference": {
    "lvl0": {
      "selector": "",
      "global": true,
      "default_value": "Flutter SDK reference"
    "lvl1": "article h1",
    "lvl2": "article h2",
    "lvl3": "article h3",
    "lvl4": "article h4",
    "lvl5": "article h5, article td:first-child",
    "lvl6": "article h6",
    "text": "article p, article li, article td:last-child"

Do I need to include an entry in the sitemap_urls section of my algolia.config.json as well? If yes, may I request some guidance about how to get a sitemap.xml that includes the content I want to index?

Thank you for any guidance you can provide!