Update pyproject.toml and readme

[steff456]

This PR,

• Fixes the pyproject.toml file to avoid build and installation errors
• Reverts a change made in the Readme in MAINT - Miscellaneous maintenance tasks #63

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pyproject.toml

This change is necessary for fixing build and installation errors using the pyproject.toml

This is one of the errors that was appearing,

The following seems to be defined outside of `pyproject.toml`:
`authors = 'quansight-labs'`
According to the spec (see the link below), however, setuptools CANNOT
consider this value unless `authors` is listed as `dynamic`.
https://packaging.python.org/en/latest/specifications/declaring-project-metadata/
For the time being, `setuptools` will still consider the given value (as a
**transitional** measure), but please note that future releases of setuptools will
follow strictly the standard.
To prevent this warning, you can list `authors` under `dynamic` or alternatively
remove the `[project]` table from your file and rely entirely on other means of
configuration.
By 2023-Oct-30, you need to update your project and remove deprecated calls
or your builds will no longer be supported.

readme

One necessary step of the local installation process was removed from the instructions

[github-actions]

👈 Launch a Binder on branch Quansight-Labs/jupyterlab-accessible-themes/steff456-patch-1

[github-actions]

👈 Launch a Binder on branch Quansight-Labs/jupyterlab-accessible-themes/steff456-patch-1

[github-actions]

👈 Launch a Binder on branch Quansight-Labs/jupyterlab-accessible-themes/steff456-patch-1

[trallard]

I am going to approve and merge, but will follow up with another PR to make some improvements