Restricting the taxonomy types shown

How would I go about only showing one - or a selection of the available - taxonomy types for editing in the admin when using the `type: taxonomy` field?

Currently, whenever this field is used, *selectize*y fields for all taxonomy types set up in `user/config/site.yaml` are shown.

The docs don't seem to make this obvious. I've figured out that if I were able to set [this `taxonomies` variable](https://github.com/getgrav/grav-plugin-admin/blob/develop/themes/grav/templates/forms/fields/taxonomy/taxonomy.html.twig#L1), this would be possible, but I can't see how to do this via my blueprint.

Start with themes/grav/templates/forms/fields/taxonomy/taxonomy.html.twig and the taxonomies variable mentioned in the issue. Check how a blueprint could control the taxonomy selection, using user/config/site.yaml as the configuration context; done means the supported configuration is documented clearly or the missing blueprint option is specified.

Written by the indexing model from the issue text.