support svg <use> elements (#612)

Author: jdanyow

src/assets/HTMLAsset.js

@@ -20,7 +20,8 @@ const ATTRS = {
     'embed'
   ],
   href: ['link', 'a'],
-  poster: ['video']
+  poster: ['video'],
+  'xlink:href': ['use']
 };
 
 class HTMLAsset extends Asset {

test/html.js

@@ -10,6 +10,11 @@ describe('html', function() {
       name: 'index.html',
       assets: ['index.html'],
       childBundles: [
+        {
+          type: 'svg',
+          assets: ['icons.svg'],
+          childBundles: []
+        },
         {
           type: 'css',
           assets: ['index.css'],

test/integration/html/icons.svg

@@ -12,5 +12,6 @@ <h1>Hello world</h1>
   <script src="index.js"></script>
   <script src="https://unpkg.com/parcel-bundler"></script>
   <i>hello</i> <i>world</i>
+  <svg><use xlink:href="icons.svg#icon-repo-pull"></use></svg>
 </body>
 </html>