[docs][calendar] Updating Calendar RecurrenceRule types and docs to functional values

[rschneid0]

This is a change from ts expecting and the docs specifying a string as the endDate of a RecurrenceRule to a number.

Why

The current calendar docs on recurrence rules are slightly inaccurate.
See #7399 for details

How

I just changed the expected type of the RecurrenceRule endDate from string to number and updated the docs accordingly.

Test Plan

This is my first PR so I'm not sure if I've touched all the appropriate files! If there's anything out of place or incomplete please let me know

[lukmccall]

Hi, @rschneid0. I'm not sure if endDate should be a number. The calendar has code that should handle 3 types: number, Date object or a string (in ISO format).

Code for reference:

• Handling strings or numbers:
  

  expo/packages/@unimodules/core/ios/UMCore/UMUtilities.m

  Lines 165 to 188 in c106d2d

  	+ (NSDate *)NSDate:(id)json
  	{
  	if ([json isKindOfClass:[NSNumber class]]) {
  	return [NSDate dateWithTimeIntervalSince1970:[json doubleValue] / 1000.0];
  	} else if ([json isKindOfClass:[NSString class]]) {
  	static NSDateFormatter *formatter;
  	static dispatch_once_t onceToken;
  	dispatch_once(&onceToken, ^{
  	formatter = [NSDateFormatter new];
  	formatter.dateFormat = @"yyyy-MM-dd'T'HH:mm:ss.SSSZZZZZ";
  	formatter.locale = [NSLocale localeWithLocaleIdentifier:@"en_US_POSIX"];
  	formatter.timeZone = [NSTimeZone timeZoneWithName:@"UTC"];
  	});
  	NSDate *date = [formatter dateFromString:json];
  	if (!date) {
  	UMLogError(@"JSON String '%@' could not be interpreted as a date. "
  	"Expected format: YYYY-MM-DD'T'HH:mm:ss.sssZ", json);
  	}
  	return date;
  	} else if (json) {
  	UMLogError(json, @"a date");
  	}
  	return nil;
  	}

• Handling Date objects:
  

  expo/packages/expo-calendar/src/Calendar.ts

  Lines 698 to 700 in c106d2d

  	function stringifyIfDate(date: any): any {
  	return date instanceof Date ? date.toISOString() : date;
  	}

So, I don't think that is a correct fix for this problem. Please check this one #7527. It should fix this bug.