How to access _data json element from the frontmatter of a template (nunjuck)

[Julianoe]

Maybe that's not the good way to do this but I'm trying to gather the maximum of settings from the project in a _data/settings.json so that the end user could customize without digging through different files and folders.

So I have created this json file, here is a sample:

{
    "title": "Collection d'images",
    "desc": "",
    "author": "Julianoë",
    "mergeSubFolders": false,
    "imagesPerPage": 10,
    "lang": "fr",

}

In a index.njk template I'd like to use the imagesPerPage parameter in the frontmatter:

---
layout: default
pagination:
  data: itemsCollection
  size: {{ settings.imagesPerPage }}
  reverse: true
permalink: "{% if pagination.pageNumber > 0 %}{{ pagination.pageNumber + 1 }}/{% endif %}index.html"
---

<section class="items">
{% for item in pagination.items %}
  {% include 'item.njk' %}
{% endfor %}
</section>
{% include 'pagination.njk' %}

When I manually enter a value in size: it works well.
But trying to use an info from the settings.json does not work.
I've tried a dozen of different syntax so I wonder: is this even possible? Or am I thinking this wrong?

Any tip would be welcome. THanks