add role="button" to [data-slide="prev"],[data-slide="next"] to improve accessibility

Per https://github.com/paypal/bootstrap-accessibility-plugin/blob/master/README.md#carousel
Credit: https://github.com/paypal/bootstrap-accessibility-plugin

docs/_includes/js/carousel.html

@@ -21,10 +21,10 @@
           <img data-src="holder.js/900x500/auto/#555:#333/text:Third slide" alt="Third slide">
         </div>
       </div>
-      <a class="left carousel-control" href="#carousel-example-generic" data-slide="prev">
+      <a class="left carousel-control" href="#carousel-example-generic" role="button" data-slide="prev">
         <span class="glyphicon glyphicon-chevron-left"></span>
       </a>
-      <a class="right carousel-control" href="#carousel-example-generic" data-slide="next">
+      <a class="right carousel-control" href="#carousel-example-generic" role="button" data-slide="next">
         <span class="glyphicon glyphicon-chevron-right"></span>
       </a>
     </div>
@@ -56,10 +56,10 @@
   </div>
 
   <!-- Controls -->
-  <a class="left carousel-control" href="#carousel-example-generic" data-slide="prev">
+  <a class="left carousel-control" href="#carousel-example-generic" role="button" data-slide="prev">
     <span class="glyphicon glyphicon-chevron-left"></span>
   </a>
-  <a class="right carousel-control" href="#carousel-example-generic" data-slide="next">
+  <a class="right carousel-control" href="#carousel-example-generic" role="button" data-slide="next">
     <span class="glyphicon glyphicon-chevron-right"></span>
   </a>
 </div>
@@ -102,10 +102,10 @@
           </div>
         </div>
       </div>
-      <a class="left carousel-control" href="#carousel-example-captions" data-slide="prev">
+      <a class="left carousel-control" href="#carousel-example-captions" role="button" data-slide="prev">
         <span class="glyphicon glyphicon-chevron-left"></span>
       </a>
-      <a class="right carousel-control" href="#carousel-example-captions" data-slide="next">
+      <a class="right carousel-control" href="#carousel-example-captions" role="button" data-slide="next">
         <span class="glyphicon glyphicon-chevron-right"></span>
       </a>
     </div>

docs/examples/carousel/index.html

@@ -113,8 +113,8 @@
           </div>
         </div>
       </div>
-      <a class="left carousel-control" href="#myCarousel" data-slide="prev"><span class="glyphicon glyphicon-chevron-left"></span></a>
-      <a class="right carousel-control" href="#myCarousel" data-slide="next"><span class="glyphicon glyphicon-chevron-right"></span></a>
+      <a class="left carousel-control" href="#myCarousel" role="button" data-slide="prev"><span class="glyphicon glyphicon-chevron-left"></span></a>
+      <a class="right carousel-control" href="#myCarousel" role="button" data-slide="next"><span class="glyphicon glyphicon-chevron-right"></span></a>
     </div><!-- /.carousel -->
 
 

docs/examples/rtl/index.html

@@ -626,10 +626,10 @@
             <img data-src="holder.js/1140x500/auto/#555:#333/text:Third slide" alt="Third slide">
           </div>
         </div>
-        <a class="left carousel-control" href="#carousel-example-generic" data-slide="prev">
+        <a class="left carousel-control" href="#carousel-example-generic" role="button" data-slide="prev">
           <span class="glyphicon glyphicon-chevron-left"></span>
         </a>
-        <a class="right carousel-control" href="#carousel-example-generic" data-slide="next">
+        <a class="right carousel-control" href="#carousel-example-generic" role="button" data-slide="next">
           <span class="glyphicon glyphicon-chevron-right"></span>
         </a>
       </div>

docs/examples/theme/index.html

@@ -628,10 +628,10 @@
             <img data-src="holder.js/1140x500/auto/#555:#333/text:Third slide" alt="Third slide">
           </div>
         </div>
-        <a class="left carousel-control" href="#carousel-example-generic" data-slide="prev">
+        <a class="left carousel-control" href="#carousel-example-generic" role="button" data-slide="prev">
           <span class="glyphicon glyphicon-chevron-left"></span>
         </a>
-        <a class="right carousel-control" href="#carousel-example-generic" data-slide="next">
+        <a class="right carousel-control" href="#carousel-example-generic" role="button" data-slide="next">
           <span class="glyphicon glyphicon-chevron-right"></span>
         </a>
       </div>