Rename package from `cofi_espresso` to `geo_espresso`

[jwhhh]

We can have the package name (on PyPI) to be different from the module name (used for import).

For example, scikit-learn is the name when we install it, and sklearn is the name to import.

So Andrew and I decided that we can have a pypi package called something like espresso-geo and then import espresso.

• Edit pyproject.toml, etc.
• Change subfolder name so that it's import espresso instead of import cofi_espresso
• Make sure all existing examples work

[valentineap]

• Move docs to espresso-geo.readthedocs.io
• Update all docs, readmes etc to reflect new names

[jwhhh]

Naming change is completed by #116. I'll close this issue after cofi-examples is updated accordingly.