adds additional context for screen reader users and correct heading order to be more logical

lms/templates/dashboard.html

@@ -77,7 +77,7 @@
 
   <section class="profile-sidebar">
     <header class="profile">
-      <h1 class="user-name">${ user.username }</h1>
+      <h2 class="user-name"><span class="sr">${_("Username")}: </span>${ user.username }</h2>
     </header>
     <section class="user-info">
       <ul>