arcgis-basemap-gallery: Organize into groups

[fdeters]

I'm wondering if the following is possible with the arcgis-basemap-gallery component (and if not, I would like to request it as a feature):

Is there a way to organize basemaps in the basemap gallery into different groups for skimming/browsing purposes?

For example, in one application, I define the `arcgis-basemap-gallery` `sources` field to be a dozen or so basemaps. Some of these are from my organization, while others are public basemaps from Living Atlas. I want to separate them into groups in the gallery so it's clear at a glance which are coming from my organization and which are coming from Living Atlas. (Note that this is just an example; the ability to manually sort them into groups arbitrarily is what I'm after.)

For my purposes, I'd need the ability to sort them into groups and title the groups:

const gallery = document.querySelector('arcgis-basemap-gallery);
await gallery.componentOnReady();

const myOrgBasemaps = [/** define some basemaps here */];
const livingAtlasBasemaps = [/** same here, but different basemaps */];

// POTENTIAL API: `source` can accept an array/Collection
// of LocalBasemapsSource, and LocalBasemapsSource supports
// a `title` property
gallery.source = [
  new LocalBasemapsSource({ 
    basemaps: myOrgBasemaps,
    title: 'Organization basemaps',
  }),
  new LocalBasemapsSource({
    basemaps: livingAtlasBasemaps,
    title: 'Living Atlas basemaps',
  }),
];

This would be a huge help for making it easier to find the right basemap!