Use link() function in template to allow adds a attributes

Problem/Motivation

Right now, "views show more pager" template creates link like:

<a href="{{ item.href }}" title="{{ 'Go to next page'|t }}" rel="next">{{ item.text }}</a>

So it is not possible to add class or other attribute using preprocessor.

Proposed resolution

Use twig link function.

{{ link(item.text, item.href, item.attributes) }}