autodetect does not identify dublincore/dcat, it assumes iso19139

dublincore is currently not available as a schema
dublin core would be nice to add, which will be quite similar as dcat

```
from pygeometa.core import import_metadata
with open('./data/cat-1/dc.xml',"r") as f:
l = import_metadata('autodetect',f.read())
```

results in:

```
Traceback (most recent call last):
File "/lib/python3.10/site-packages/pygeometa/core.py", line 352, in import_metadata
return schema_object.import_(metadata)
File "/lib/python3.10/site-packages/pygeometa/schemas/iso19139/__init__.py", line 110, in import_
identification = m.identification[0]
IndexError: list index out of range
```

[dc-ds.xml](https://github.com/user-attachments/files/22276621/dc-ds.xml)

owslib supports dublin core imports https://owslib.readthedocs.io/en/latest/usage.html#dublin-core, not sure to what extend, DC below is generated with https://nsteffel.github.io/dublin_core_generator/generator_nq.html

[dc3.xml](https://github.com/user-attachments/files/22276696/dc3.xml)