Render media in posts

Closes #8

lib/pages/article.dart

@@ -109,9 +109,11 @@ class _ArticlePageState extends State<ArticlePage> {
         children: [
           Container(
             margin: const EdgeInsets.all(12.0),
-            child: SelectableHtml(
+            child: SelectionArea(
+              child: Html(
                 data: widget.article.html,
               ),
+            ),
           )
         ],
       ),