[RFC] add prev/next classes to pager

[peterboorsma]

The out-of-the-box implementation of the pagination functionality could do with some additional classnames to make life easier for frontenders :)
I'd like to add classes to the next buttons.

Basic Bolt

<ul class="pagination">
    <li disabled="disabled"><a disabled="disabled">Previous</a></li>
    <li class=" active"><a aria-current="page" href="/blogs?page=1">1</a></li>
    <li><a href="/blogs?page=2">2</a></li>
    <li><a href="/blogs?page=7">7</a></li>
    <li><a href="/blogs?page=2">Next</a></li>
</ul>

Proposal

<ul class="pagination">
    <li class="previous" disabled="disabled"><a disabled="disabled">Previous</a></li>
    <li class=" active"><a aria-current="page" href="/blogs?page=1">1</a></li>
    <li><a href="/blogs?page=2">2</a></li>
    <li><a href="/blogs?page=7">7</a></li>
    <li class="next"><a href="/blogs?page=2">Next</a></li>
</ul>