Releasing the ElCat CLDF data

Remove the results of the last web-crawl:
```
rm -rf raw/html
```
Crawl the website:
```
cldfbench download cldfbench_elcat.py
```

Re-create the CLDF data:

cldfbench makecldf --with-zenodo --with-cldfreadme cldfbench_elcat.py --glottolog-version v4.7

Validate the data:
```
pytest
```

Make sure an SQLite database can be created:

rm -f elcat.sqlite
cldf createdb cldf/StructureDataset-metadata.json elcat.sqlite

Re-create the README:
```
cldfbench readme cldfbench_elcat.py
```
Commit, tag, push.
Create a release on GitHub