Merge pull request #14579 from twbs/accordion-heading-role-tab

add role="tab" to .panel-heading-s in accordion example to improve accessibility

diff --cc docs/_includes/js/collapse.html
index 5239256a62012a69d9fccc9f505b0f8d1a637e9a,a69fb57e14d16a8aa5ada7f5a23d36418eae7f59..66c6254f9fb970927ffc8fcaedc30ec45c49a391
--- 1/docs/_includes/js/collapse.html
--- 2/docs/_includes/js/collapse.html
+++ b/docs/_includes/js/collapse.html
@@@ -15,9 -15,9 +15,9 @@@
    <div class="bs-example">
      <div class="panel-group" id="accordion" role="tablist" aria-multiselectable="true">
        <div class="panel panel-default">
-         <div class="panel-heading">
+         <div class="panel-heading" role="tab">
            <h4 class="panel-title">
 -            <a data-toggle="collapse" data-parent="#accordion" href="#collapseOne">
 +            <a data-toggle="collapse" data-parent="#accordion" href="#collapseOne" aria-expanded="true" aria-controls="collapseOne">
                Collapsible Group Item #1
              </a>
            </h4>
@@@ -29,9 -29,9 +29,9 @@@
          </div>
        </div>
        <div class="panel panel-default">
-         <div class="panel-heading">
+         <div class="panel-heading" role="tab">
            <h4 class="panel-title">
 -            <a data-toggle="collapse" data-parent="#accordion" href="#collapseTwo">
 +            <a data-toggle="collapse" data-parent="#accordion" href="#collapseTwo" aria-expanded="false" aria-controls="collapseTwo">
                Collapsible Group Item #2
              </a>
            </h4>
@@@ -43,9 -43,9 +43,9 @@@
          </div>
        </div>
        <div class="panel panel-default">
-         <div class="panel-heading">
+         <div class="panel-heading" role="tab">
            <h4 class="panel-title">
 -            <a data-toggle="collapse" data-parent="#accordion" href="#collapseThree">
 +            <a data-toggle="collapse" data-parent="#accordion" href="#collapseThree" aria-expanded="false" aria-controls="collapseThree">
                Collapsible Group Item #3
              </a>
            </h4>
@@@ -61,9 -61,9 +61,9 @@@
  {% highlight html %}
  <div class="panel-group" id="accordion" role="tablist" aria-multiselectable="true">
    <div class="panel panel-default">
-     <div class="panel-heading">
+     <div class="panel-heading" role="tab">
        <h4 class="panel-title">
 -        <a data-toggle="collapse" data-parent="#accordion" href="#collapseOne">
 +        <a data-toggle="collapse" data-parent="#accordion" href="#collapseOne" aria-expanded="true" aria-controls="collapseOne">
            Collapsible Group Item #1
          </a>
        </h4>
@@@ -75,9 -75,9 +75,9 @@@
      </div>
    </div>
    <div class="panel panel-default">
-     <div class="panel-heading">
+     <div class="panel-heading" role="tab">
        <h4 class="panel-title">
 -        <a data-toggle="collapse" data-parent="#accordion" href="#collapseTwo">
 +        <a data-toggle="collapse" data-parent="#accordion" href="#collapseTwo" aria-expanded="false" aria-controls="collapseTwo">
            Collapsible Group Item #2
          </a>
        </h4>
@@@ -89,9 -89,9 +89,9 @@@
      </div>
    </div>
    <div class="panel panel-default">
-     <div class="panel-heading">
+     <div class="panel-heading" role="tab">
        <h4 class="panel-title">
 -        <a data-toggle="collapse" data-parent="#accordion" href="#collapseThree">
 +        <a data-toggle="collapse" data-parent="#accordion" href="#collapseThree" aria-expanded="false" aria-controls="collapseThree">
            Collapsible Group Item #3
          </a>
        </h4>