Add tasks for all the new languages

Task/Hello-world-Graphical/Sidef/hello-world-graphical-1.sidef

@@ -0,0 +1,7 @@
+var tk = require('Tk');
+var main = %s'MainWindow'.new;
+main.Button(
+    '-text'    => 'Goodbye, World!',
+    '-command' => 'exit',
+).pack;
+tk.MainLoop;

Task/Hello-world-Graphical/Sidef/hello-world-graphical-2.sidef

@@ -0,0 +1,12 @@
+var gtk2 = require('Gtk2') -> init;
+
+var window = %s'Gtk2::Window'.new;
+var label  = %s'Gtk2::Label'.new('Goodbye, World!');
+
+window.set_title('Goodbye, World!');
+window.signal_connect(destroy => func(*_){ gtk2.main_quit });
+
+window.add(label);
+window.show_all;
+
+gtk2.main;