Add Norway dataset to repository

[khsjursen]

Add available cleaned/preprocessed datasets to repository from Norway.

Source: https://nva.sikt.no/registration/01953ca70ea8-d0d31171-7b4d-4271-9d93-1291f4133b08
Elvehøy, H., Kjøllmoen, B., Andreassen, L. M., and Sjursen, K. H.: Glaciological point mass balance measurements for Norway 1962-2021, Norwegian Water Resources and Energy Directorate (NVE), Oslo, Norway, https://doi.org/10.58059/sjse-6w92, 2025

Cleaned datasets should have the following columns:

FROM_DATE
TO_DATE
POINT_LAT
POINT_LON
POINT_BALANCE
POINT_ELEVATION
(POINT_ID) ```