Implement support for historical date

This branch is to implement support for BCE/BC and CE/AD dates.
This implementation cover only the Year and will not works with month, day etc.

Note:

Implementation was done only with the added test to verify it's working. Maybe some additional testing would be needed

Changes

• Add regex for the BCE dates
• Add case where needed to parse BCE dates
• Add Method to get Datetime from a year and its notation to cover that year 0 doesn't exist (we go from 1BCE to 1AD) but in javascript year 0 exist
• Add Tests

Known issues:

• AD dates are supposed to be formatted with AD then Year (AD 70). For simplicity and to align with other notation AD should be after the year: "5 AD: Some event"
• Currently you cannot mix and match EDF/Event dates and BCE dates. It means you cannot have something like: "250BC - 01/01/70". You need to set "70 AD" or "70 CE"

Example:

Refer to tests/dates.test.ts to see some examples

Tests result:

Failing test are already failing on main branch:

# main branch
Test Suites: 2 failed, 5 passed, 7 total
Tests:       4 failed, 12 skipped, 476 passed, 492 total
Snapshots:   0 total
Time:        9.793 s

This branch

 PASS  tests/regex.test.ts (5.256 s)
 FAIL  tests/ical.test.ts (5.45 s)
 PASS  tests/recurrence.test.ts (5.455 s)
 PASS  tests/dates.test.ts (5.605 s)
 PASS  tests/entryProperties.test.ts (5.509 s)
 PASS  tests/zones.test.ts (5.568 s)
 FAIL  tests/header.test.ts (5.641 s)
 PASS  tests/main.test.ts (6.067 s)
 
Test Suites: 2 failed, 6 passed, 8 total
Tests:       4 failed, 12 skipped, 489 passed, 505 total
Snapshots:   0 total
Time:        6.788 s, estimated 7 s