Theme description key in blueprints.yaml doesn't lookup translation

In my theme's blueprints.yaml, the `description` key doesn't lookup translations set in languages.yaml (or in languages/fr.yaml, I tried both setup).

Here is the result:

blueprints.yaml (the `...` are an ellipsis for multiple other keys)

```yaml
name: Boite A Cycler
version: 0.0.1
description: BOITEACYCLER.THEME_DESCRIPTION
...
```

languages.yaml

```yaml
BOITEACYCLER:
THEME_DESCRIPTION: "Le thème de l'association Boite à Cycler"
...
```

Start with the theme blueprints.yaml and the languages.yaml or languages/fr.yaml examples in the issue, then reproduce the untranslated description in the Grav Admin Plugin. Trace how the blueprint description is loaded and how translation keys are resolved; done means BOITEACYCLER.THEME_DESCRIPTION displays its translated value.

Written by the indexing model from the issue text.