rewrite some button group docs

docs/getting-started/accessibility.md

@@ -6,6 +6,20 @@ group: getting-started
 
 Bootstrap follows common web standards and—with minimal extra effort—can be used to create sites that are accessible to those using <abbr title="Assistive Technology" class="initialism">AT</abbr>.
 
+## Component requirements
+
+Some common HTML elements are always in need for basic accessibility enhancements through `role`s and Aria attributes. Below is a list of some of the most frequently used ones.
+
+{% callout info %}
+**Heads up!** As we go through the alphas, we'll be moving more accessibility notes here with links to specific sections from other areas of the docs.
+{% endcallout %}
+
+### Button groups
+
+In order for assistive technologies–such as screen readers–to convey that a series of buttons is grouped, an appropriate `role` attribute needs to be provided. For button groups, this would be `role="group"`, while toolbars should have a `role="toolbar"`.
+
+In addition, groups and toolbars should be given an explicit label, as most assistive technologies will otherwise not announce them, despite the presence of the correct `role` attribute. In the examples provided here, we use `aria-label`, but alternatives such as `aria-labelledby` can also be used.
+
 ## Skip navigation
 
 If your navigation contains many links and comes before the main content in the DOM, add a `Skip to main content` link before the navigation (for a simple explanation, see this [A11Y Project article on skip navigation links](http://a11yproject.com/posts/skip-nav-links/)). Using the `.sr-only` class will visually hide the skip link, and the <code>.sr-only-focusable</code> class will ensure that the link becomes visible once focused (for sighted keyboard users).