Add territories Svalbard and Jan Mayen (SJ)

The following list of holidays needs to be verified/completed:
|Date | Flags | Name|
| --- | --- | --- |
| 01-01 | [NF] | Nyttårsdag |
| 05-01 | [NF] | Offentlig Høytidsdag |
| 05-08 | [NF] | Frigjøringsdag 1945 |
| 05-17 | [NF] | Grunnlovsdag |
| 12-24 | [NRF] | Julaften |
| 12-25 | [NRF] | Juledag |
| 12-26 | [NRF] | Juledag |
| 12-31 | [NF] | Nyttårsaften |
| | [NRV] | Fastelavn |
| | [NRV] | Palmesøndag |
| | [NRV] | Skjærtorsdag |
| | [NRV] | Langfredag |
| | [NRV] | Påskedag |
| | [NRV] | Påskedag |
| | [NRV] | Kristi Himmelfartsdag |
| | [NRV] | Pinsedag |
| | [NRV] | Pinsedag |

Checklist:
* What type is the easter date?
- [ ] orthodox
- [x] western
- [ ] All holidays (i.e. days "which are defined by law on which business or work are suspended or reduced") are listed
- [ ] Legal sources which define the holidays are provided
- [ ] The spelling of the holiday names is correct
- [ ] The given dates (independent of year) of the holidays are correct

Start by locating the existing territory holiday definitions and the tests or entry points used for calendar data, then compare the Svalbard and Jan Mayen list with authoritative legal sources. Done means the SJ territory is represented with verified holiday names, fixed dates, western Easter-based dates, and source references.

Written by the indexing model from the issue text.