fix(a11y): minor markup fix to improve breadcrumb semantics (#263)

Author: chrisdhanaraj

src/components/breadcrumb/breadcrumb.html

@@ -1,4 +1,4 @@
-<div class="bx--breadcrumb bx--breadcrumb--no-trailing-slash">
+<nav class="bx--breadcrumb bx--breadcrumb--no-trailing-slash" aria-label="breadcrumb">
   <div class="bx--breadcrumb-item">
     <a href="#" class="bx--link">Breadcrumb 1</a>
   </div>
@@ -11,5 +11,4 @@
   <div class="bx--breadcrumb-item">
     <span>Breadcrumb 4</span>
   </div>
-</div>
-
+</nav>