Expose media_tag and other taxonomies to wpgraphql

It looks like the taxonomies created with TaxoPress aren’t exposed in wpgraphql under the regular taxonomies:

query Taxonomy {
  taxonomies {
    nodes {
      description
      id
      name
      label
      public
    }
  }
}

// returns the following when TaxoPress is enabled:
{
  "data": {
    "taxonomies": {
      "nodes": [
        {
          "description": "",
          "id": "dGF4b25vbXk6Y2F0ZWdvcnk=",
          "name": "category",
          "label": null,
          "public": null
        },
        {
          "description": "",
          "id": "dGF4b25vbXk6cG9zdF90YWc=",
          "name": "post_tag",
          "label": null,
          "public": null
        },
        {
          "description": "",
          "id": "dGF4b25vbXk6cG9zdF9mb3JtYXQ=",
          "name": "post_format",
          "label": null,
          "public": null
        }
      ]
    }
  },
}

However you can expose the taxonomy by registering it to show in GraphQL. This may be good to add to the plugin documentation for others:

function register_media_tag_graphql()
{
	register_taxonomy('media_tag', 'attachment', array(
		'show_in_graphql' => true,
		'graphql_single_name' => 'MediaTag',
		'graphql_plural_name' => 'MediaTags',
	));
}
add_action('init', 'register_media_tag_graphql');

Now I can query the tags from the taxoPress taxonomy:

query MediaTags {
  mediaTags {
    nodes {
      databaseId
      name
      slug
      taxonomyName
    }
  }
}

// returns:
{
  "data": {
    "mediaTags": {
      "nodes": [
        {
          "databaseId": 7,
          "name": "los angeles",
          "slug": "los-angeles",
          "taxonomyName": "media_tag"
        },
        {
          "databaseId": 6,
          "name": "toronto",
          "slug": "toronto",
          "taxonomyName": "media_tag"
        }
      ]
    }
  },
}