List Organization theme summaries

{  "$schema": "https://example.com/api/v1/schemas/ThemeSummaryPage.json",  "items": [    {      "assigned_workspace_count": 0,      "built_in": true,      "created_at": "2019-08-24T14:15:22Z",      "description": "string",      "draft_revision": 0,      "icon_pack": "lucide",      "is_organization_default": true,      "name": "string",      "organization_id": "string",      "published_revision": 0,      "reference": {        "id": "string",        "kind": "built_in",        "version": 1      },      "supported_schemes": [        "light"      ],      "updated_at": "2019-08-24T14:15:22Z"    }  ],  "next_cursor": "string"}