views: move agenda view to main area

This prepares for multiple views to be there for mobile
users, and is the location at which a dedicated agenda
view for desktop will be, once the current agenda view
is refactored to suit desktop use-cases better.

Signed-off-by: Markus Göllnitz <camelcasenick@bewares.it>
Part-of: <https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/542>

src/gcal-enums.h

@@ -35,6 +35,7 @@ typedef enum
  * GcalWindowViewType:
  * @GCAL_WINDOW_VIEW_WEEK: Week view
  * @GCAL_WINDOW_VIEW_MONTH: Month view
+ * GCAL_WINDOW_VIEW_AGENDA: Agenda/list view
  *
  * Enum with the available views.
  */
@@ -42,6 +43,7 @@ typedef enum
 {
   GCAL_WINDOW_VIEW_WEEK,
   GCAL_WINDOW_VIEW_MONTH,
+  GCAL_WINDOW_VIEW_AGENDA,
 
   GCAL_WINDOW_VIEW_N_VIEWS,
 } GcalWindowView;