[IMP] web, project, base: move project calendar task planning to web

This commit adds documentation support for the new calendar view attribute
introduced in odoo/odoo#238557

task-5364034

Author: juliusc2066

content/developer/reference/user_interface/view_architectures.rst

@@ -3334,6 +3334,17 @@ Their root element is ``<calendar>``. Available attributes on the root node are:
    :type: bool
    :default: `True`
 
+.. attribute:: schedule
+   :noindex:
+
+   If set to `True`, non-scheduled events (events which have their start date and 
+   stop date unset) will appear in the side-panel so that the user can drag and drop
+   these events into the calendar in order to schedule them instantaneously.
+
+   :requirement: Optional
+   :type: bool
+   :default: `False`
+
 .. attribute:: event_open_popup
    :noindex: