(core) Add tip for calendar widget configuration

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

app/common/Prefs.ts

@@ -87,6 +87,7 @@ export const BehavioralPrompt = StringUnion(
   'addNew',
   'rickRow',
   'customURL',
+  'calendarConfig',
 );
 export type BehavioralPrompt = typeof BehavioralPrompt.type;
 

app/common/gristUrls.ts

@@ -79,6 +79,7 @@ export const commonUrls = {
   helpTryingOutChanges: "https://support.getgrist.com/copying-docs/#trying-out-changes",
   helpCustomWidgets: "https://support.getgrist.com/widget-custom",
   helpTelemetryLimited: "https://support.getgrist.com/telemetry-limited",
+  helpCalendarWidget: "https://support.getgrist.com/widget-calendar",
   plans: "https://www.getgrist.com/pricing",
   sproutsProgram: "https://www.getgrist.com/sprouts-program",
   contact: "https://www.getgrist.com/contact",