Improving example of modular button classes

Links and buttons have different semantic html meanings, and it is somewhat of a design (and accessibility) anti-pattern to style links as a button

docs/documentation/overview/modular.html

@@ -31,21 +31,21 @@ breadcrumb:
 {% endcapture %}
 
 {% capture buttons %}
-<a class="button">
+<button class="button">
   Button
-</a>
+</button>
 
-<a class="button is-primary">
+<button class="button is-primary">
   Primary button
-</a>
+</button>
 
-<a class="button is-large">
+<button class="button is-large">
   Large button
-</a>
+</button>
 
-<a class="button is-loading">
+<button class="button is-loading">
   Loading button
-</a>
+</button>
 {% endcapture %}
 
 <div class="content">