add link to MDN docs regarding iOS Safari element clickability

docs/_includes/getting-started/browser-device-support.html

@@ -160,7 +160,7 @@ if (navigator.userAgent.match(/IEMobile\/10\.0/)) {
   <h4>Virtual keyboards</h4>
   <p>Also, note that if you're using a fixed navbar or using inputs within a modal, iOS has a rendering bug that doesn't update the position of fixed elements when the virtual keyboard is triggered. A few workarounds for this include transforming your elements to <code>position: absolute</code> or invoking a timer on focus to try to correct the positioning manually. This is not handled by Bootstrap, so it is up to you to decide which solution is best for your application.</p>
   <h4>Navbar Dropdowns</h4>
-  <p>The <code>.dropdown-backdrop</code> element isn't used on iOS in the nav because of the complexity of z-indexing. Thus, to close dropdowns in navbars, you must directly click the dropdown element (or any other element which will fire a click event in iOS).</p>
+  <p>The <code>.dropdown-backdrop</code> element isn't used on iOS in the nav because of the complexity of z-indexing. Thus, to close dropdowns in navbars, you must directly click the dropdown element (or <a href="https://developer.mozilla.org/en-US/docs/Web/Events/click#Safari_Mobile">any other element which will fire a click event in iOS</a>).</p>
 
   <h3 id="support-browser-zooming">Browser zooming</h3>
   <p>Page zooming inevitably presents rendering artifacts in some components, both in Bootstrap and the rest of the web. Depending on the issue, we may be able to fix it (search first and then open an issue if need be). However, we tend to ignore these as they often have no direct solution other than hacky workarounds.</p>