feat: implement the base classes for launcher + input

- Base classes for lancher: Dashboard + Taskbar
- Allow the shell to monitor directly wayland seat keyboard (on demand)

resources/session-shell.css

@@ -1,9 +1,15 @@
 @import url("resource:///dev/iohub/diya/shell/virtual-keyboard.css");
 
-#diya_shell_launcher
+diya-taskbar
 {
     background-color: orange;
 }
+
+diya-dashboard
+{
+    background-color: blue;
+}
+
 #diya_shell_background
 {
     background-image:url("file:///etc/xdg/labwc/wpp.jpg");