Button responsive block

<!-- Source -->
<button class="btn btn-secondary btn-sm-block" type="button">Button</button>
<button class="btn btn-secondary btn-md-block" type="button">Button</button>
<button class="btn btn-secondary btn-lg-block" type="button">Button</button>
<button class="btn btn-secondary btn-xl-block" type="button">Button</button>