Add park-and-ride opening hours (AvailabilityCondition) example on Parking

[teppope]

Summary

Adds an example of AvailabilityCondition (opening hours) on a Parking element, showing a per-day-type pattern: open 06:00–22:00 on business days and Saturdays, closed on Sundays.

This illustrates the NeTEx Nordic profile extension proposed by Fintraffic to support park-and-ride opening hours — see the CCB proposal:
https://finrail.atlassian.net/wiki/spaces/VACO1/pages/4838883341

Note: this PR depends on the CCB proposal above being approved. It is opened as a draft now to have the example ready; please do not merge until the proposal has been accepted by the Nordic CCB. Related Jira: DPO-4787 (CCB submission, not yet submitted), DPO-4788 (this documentation task).

What changed

• netex/stops/StopPlace-with-equipment-and-parking_example.xml: added a validityConditions/AvailabilityCondition block (with IsAvailable, dayTypes/DayTypeRef, and timebands/Timeband) to the first Parking element (NSR:Parking:1), following the existing element/property order defined by EntityInVersionGroup (validated against the netex-java-model JAXB classes — validityConditions is the first child element of Parking, ahead of levels/entrances/etc.).

Validation

• Verified well-formed XML.
• Validated the whole file against the full NeTEx 1.13 XSD bundled in org.entur:netex-java-model (the same schema Tiamat uses for NeTEx import) using xmllint. The added block produces zero validation errors. Three pre-existing, unrelated schema errors already present in the file before this change (enum value casing drift in ScopeOfTicketsAvailable/SanitaryFacilityList, unrelated to Parking) were left untouched, per scope.