Add calendar, refactor more

src/widgets/mod.rs

@@ -1,6 +1,7 @@
 mod backlight;
 mod bar_widget;
 mod battery;
+mod calendar;
 mod clock;
 mod date;
 mod launcher;
@@ -9,11 +10,12 @@ mod widget;
 
 pub use backlight::Backlight;
 pub use battery::Battery;
+pub use calendar::Calendar;
 pub use clock::Clock;
 pub use date::Date;
 pub use launcher::Interface;
 pub use line::Line;
 pub use widget::{
-    Geometry, HorizontalLayout, IndexedLayout, Layout, Margin, VerticalLayout, Widget,
-    WidgetUpdater,
+    Geometry, HorizontalLayout, IndexedLayout, InvertedHorizontalLayout, Layout, Margin,
+    VerticalLayout, Widget, WidgetUpdater,
 };