gluing doesn't seem to work with nested folders

[jbogaardt]

Hi,

I am trying to create a figure in a subfolder of my docs, .../docs/folder1/notebook.ipynb using the following syntax:

from myst_nb import glue
glue("subfolder_image", ax.get_figure(), display=False)

Then I try to reference the figure in docs/intro.ipynb, at the parent folder level using:

```{glue:} subfolder_image
```

The rendered docs wants to grab it from the root .../docs/_build/jupyter_execute/sample_figure_7_0.svg.
But it doesn't exist there. It is at .../docs/_build/jupyter_execute/folder1/sample_figure_7_0.svg and so it is not finding the image correctly.

Sadly for me, doing this doesn't work:

```{glue:} folder1/subfolder_image
```

Is it not possible to use glue with nested folders?