Added the ability to assign shortcuts to all bar modules. (#278)

lib/types/bar.d.ts

@@ -1,7 +1,7 @@
 import { Binding, Connectable } from 'types/service';
 import { Variable } from 'types/variable';
 import Box from 'types/widgets/box';
-import Button from 'types/widgets/button';
+import Button, { ButtonProps } from 'types/widgets/button';
 import Label from 'types/widgets/label';
 import { Attribute, Child } from './widget';
 
@@ -10,7 +10,9 @@ export type BarBoxChild = {
     isVisible?: boolean;
     isVis?: Variable<boolean>;
     boxClass: string;
-} & ButtonProps;
+    tooltip_text?: string | Binding<string>;
+    props: ButtonProps;
+};
 
 export type SelfButton = Button<Child, Attribute>;