Give all embedded live docs examples data-example-id attrs

Refs #11410

docs/_includes/components/button-dropdowns.html

@@ -10,7 +10,7 @@
 
   <h3 id="btn-dropdowns-single">Single button dropdowns</h3>
   <p>Turn a button into a dropdown toggle with some basic markup changes.</p>
-  <div class="bs-example">
+  <div class="bs-example" data-example-id="single-button-dropdown">
     <div class="btn-group">
       <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown" aria-expanded="false">Default <span class="caret"></span></button>
       <ul class="dropdown-menu" role="menu">
@@ -90,7 +90,7 @@
 
   <h3 id="btn-dropdowns-split">Split button dropdowns</h3>
   <p>Similarly, create split button dropdowns with the same markup changes, only with a separate button.</p>
-  <div class="bs-example">
+  <div class="bs-example" data-example-id="split-button-dropdown">
     <div class="btn-group">
       <button type="button" class="btn btn-default">Default</button>
       <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown" aria-expanded="false">
@@ -196,7 +196,7 @@
 
   <h3 id="btn-dropdowns-sizing">Sizing</h3>
   <p>Button dropdowns work with buttons of all sizes.</p>
-  <div class="bs-example">
+  <div class="bs-example" data-example-id="button-dropdown-sizing">
     <div class="btn-toolbar" role="toolbar">
       <div class="btn-group">
         <button class="btn btn-default btn-lg dropdown-toggle" type="button" data-toggle="dropdown" aria-expanded="false">
@@ -274,7 +274,7 @@
 
   <h3 id="btn-dropdowns-dropup">Dropup variation</h3>
   <p>Trigger dropdown menus above elements by adding <code>.dropup</code> to the parent.</p>
-  <div class="bs-example">
+  <div class="bs-example" data-example-id="button-dropdown-dropup">
     <div class="btn-toolbar" role="toolbar">
       <div class="btn-group dropup">
         <button type="button" class="btn btn-default">Dropup</button>