Add more loading methods

src/lib/MarkdownView.vala

@@ -66,6 +66,24 @@ namespace GtkCommonMark {
             reader.read_data(data);
         }
 
+        public async void load_from_stream_async(InputStream stream) throws IOError {
+            var reader = new GtkCommonMark.Reader(buffer, this, tag_manager);
+            reader.widget_embedded.connect(on_widget_embedded);
+            
+            MemoryOutputStream os = new MemoryOutputStream (null, GLib.realloc, GLib.free);
+            yield os.splice_async (stream, OutputStreamSpliceFlags.CLOSE_TARGET, Priority.DEFAULT);
+            var data = os.steal_data();
+            data.length = (int) os.get_data_size ();
+            reader.read_data(data);
+        }
+
+        public void load_from_string(string markdown) {
+            var reader = new GtkCommonMark.Reader(buffer, this, tag_manager);
+            reader.widget_embedded.connect(on_widget_embedded);
+            
+            reader.read_data((uint8[])markdown.to_utf8());
+        }
+
         protected string? link_at_buffer_location(int x, int y) {
             Gtk.TextIter iter;
             get_iter_at_location(out iter, x, y);