refs #35: add title on tap

lib/src/channel_header.dart

@@ -57,11 +57,15 @@ class ChannelHeader extends StatelessWidget implements PreferredSizeWidget {
   /// By default it calls [Navigator.pop]
   final VoidCallback onBackPressed;
 
+  /// Callback to call when pressing the header is tapped.
+  final VoidCallback onTitleTap;
+
   /// Creates a channel header
   ChannelHeader({
     Key key,
     this.showBackButton = true,
     this.onBackPressed,
+    this.onTitleTap,
   })  : preferredSize = Size.fromHeight(kToolbarHeight),
         super(key: key);
 
@@ -86,8 +90,14 @@ class ChannelHeader extends StatelessWidget implements PreferredSizeWidget {
         ),
       ],
       centerTitle: true,
-      title: Column(
+      title: InkWell(
+        onTap: () {},
+        child: Container(
+          height: preferredSize.height,
+          width: preferredSize.width,
+          child: Column(
             crossAxisAlignment: CrossAxisAlignment.center,
+            mainAxisAlignment: MainAxisAlignment.center,
             children: <Widget>[
               ChannelName(
                 textStyle: StreamChatTheme.of(context)
@@ -98,6 +108,8 @@ class ChannelHeader extends StatelessWidget implements PreferredSizeWidget {
               _buildLastActive(context, channel),
             ],
           ),
+        ),
+      ),
     );
   }