Summary:
The tip is shown in the creator panel, in the subtab that lists the column
mapping configuration for the calendar widget. The panel now automatically
opens the first time a calendar widget is added to a page (via the Add New menu).
Test Plan: Manual.
Reviewers: JakubSerafin
Reviewed By: JakubSerafin
Subscribers: JakubSerafin, jarek
Differential Revision: https://phab.getgrist.com/D4047
