Adapt repo to submission on 4TU.ResearchData

[cforgaci]

We decided not to publish on CRAN anymore (see #9) and to release the example data on 4TU.ResearchData. This repo contains the pacakge we used to generate the example data. Things to do to wrap this up:

• Remove CRAN submission artefacts
• Generate the example data in GPKG and GeoTIFF formats as well
• Rename the repository into CRiSpExampleData and update package metadata accordingly
• Add link to this repo in the data publication on 4TU.RD
• Create GitHub release