Add customer info to cart object

cart.json.liquid

{% layout none %}

{% assign data = cart | json %}
{% assign customer_name = customer.first_name | json %}

{% comment %}
  // Or is there a merge filter in liquify??
  {% assign mergeData = data | merge({'customer_name': customer_name}) %}
  {{ mergeData }}
{% endcomment %}


{% if shop.customer_accounts_enabled %}
  {% if customer %}
    {% assign data.customer_name = customer_name %}
  {% endif %}
{% endif %}

{{ data }}