Add syntax: {% include 'template' with {var: 2, var2: 'b'} %}

This is useful for re-using bits of HTML that have small changes, for example a search box used on multiple pages with different placeholder text:

`{% include 'search-box.html.twig' with {placeholder: 'Search users'} %}`

`{% include 'search-box.html.twig' with {placeholder: 'Search companies'} %}`

This isn't a feature of jinja, but is a feature of the similar Twig framework.