Use in-memory catalog for demo

[kevinjqliu]

Great project! Just went through the setup process and thought it'd be a good idea to use an in-memory catalog for demo.
Here's an example of an in-memory catalog
https://github.com/apache/iceberg-python/blob/9857107561d2267813b7ce150b01b4e6ac4b3e34/tests/catalog/test_sql.py#L113-L117

This requires pyiceberg[sql-sqlite]
https://github.com/apache/iceberg-python/blob/9857107561d2267813b7ce150b01b4e6ac4b3e34/pyproject.toml#L595

[rakeshJn]

Thanks @kevinjqliu , sure we will try it out, or, please feel free to add it yourself.