Add the {% with %} tag

[jg-rp]

Add an implementation of the {% with %} tag.

The with tag extends the template namespace with block scoped variables. These variables have the potential to temporarily shadow global variables or variables assigned with {% assign %} and {% capture %}.

{% with p: collection.products.first %}
  {{ p.title }}
{% endwith %}

{% with a: 1, b: 3.4 %}
  {{ a }} + {{ b }} = {{ a | plus: b }}
{% endwith %}