feat: start work to name the new-look package 'kaleido2'

[gvwilson]

Note: fails some tests - see below.

1. Modify ./README.md and copy it into ./src/py/README.md.
   • Because Python packaging won't let me include ../../README.md in pyproject.toml.
2. Add diagram in assets/architecture.svg showing the old and new designs.
   • Created with the desktop version of draw.io.
3. Rename src/py/kaleido as src/py/kaleido2.
4. Modify src/py/pyproject.toml to rename package.
5. Edit src/py/kaleido2/__init__.py to change kaleido to kaleido2.
   • FIXME: I have left environment variables and JS stuff as kaleido - should this change?
6. Edit src/py/kaleido2/scopes/plotly.py to refer to kaleido2 instead of kaleido.

After doing all of this, go into src/py and:

1. uv venv and activate the virtual environment (using Python 3.12.5).
2. uv pip install -e . to create editable install.
3. uv pip install plotly pandas so that manual tests will run.
4. python tests/manual.py to run manual tests.

Output is as shown below: 7 tests fail with the same error; I presume we're going to have to make changes to plotly.py to pick up kaleido2.

python tests/manual.py
Done!
Successes: 28/35
Errors:
[
  ValueError('\nImage export using the "kaleido" engine requires the kaleido package,\nwhich can be installed using pip:\n    $ pip install -U kaleido\n'),
  ValueError('\nImage export using the "kaleido" engine requires the kaleido package,\nwhich can be installed using pip:\n    $ pip install -U kaleido\n'),
  ValueError('\nImage export using the "kaleido" engine requires the kaleido package,\nwhich can be installed using pip:\n    $ pip install -U kaleido\n'),
  ValueError('\nImage export using the "kaleido" engine requires the kaleido package,\nwhich can be installed using pip:\n    $ pip install -U kaleido\n'),
  ValueError('\nImage export using the "kaleido" engine requires the kaleido package,\nwhich can be installed using pip:\n    $ pip install -U kaleido\n'),
  ValueError('\nImage export using the "kaleido" engine requires the kaleido package,\nwhich can be installed using pip:\n    $ pip install -U kaleido\n'),
  ValueError('\nImage export using the "kaleido" engine requires the kaleido package,\nwhich can be installed using pip:\n    $ pip install -U kaleido\n')
]
Please send over test-results.zip
Logs and images in ./test-results/

test-results.zip