[Block] Expose network/multisite as a setting

Currently, on the PHP end (via direct use or filter), you can set the `network` for the `Builder`, which will show the network home link as part of the breadcrumb trail. For example:

```php
new Builder($environment, [
	'network' => true
]);
```

This option should be exposed for sites in a multisite installation as a toggle switch to enable the link.