Add explicit links to data for tutorial notebooks

As pointed out here, it is not clear where the input files for the tutorials can be found.

The peak fitting tutorial and the ACF tutorial use data included in the repo, see here and here, respectively.

The output files could be made available via zenodo. At the least it should be pointed out where to find the data

For the SED tutorial the input files can be found in the repo. Users must conduct the runs themselves in order to have the output files. It would be better to provide the input files and also the output files via zenodo.

Todos

• generate output files for SED tutorial
• upload files for all tutorial to zenodo; see https://zenodo.org/records/17858255
• update tutorial notebooks to use wget
• remove files from repo