Phase out tox

[marco-2023]

Grid was using pyproject.toml and tox.ini as duplicated sources of truth for package configuration.
This PR sets pyproject.toml as the only source of truth.

[Copilot]

Pull request overview

This PR aims to remove duplicated packaging/QA configuration by phasing out tox.ini/requirements.txt and consolidating configuration in pyproject.toml, while also updating docs/code to match the new baseline (Python 3.10+, Ruff, stdlib importlib.resources).

Changes:

• Remove legacy tooling/config files (tox.ini, requirements.txt) and move related config into pyproject.toml (extras, Ruff, Coverage, Pytest).
• Update code to use importlib.resources.files (dropping importlib_resources).
• Refresh documentation/README (installation instructions, citation info, CI badge text).

Reviewed changes

Copilot reviewed 12 out of 13 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tox.ini	Deleted tox-based env configuration.
requirements.txt	Deleted legacy requirements file.
pyproject.toml	Becomes primary source of truth (deps/extras + Ruff/Coverage/Pytest config); raises minimum Python.
src/grid/tests/test_cubic.py	Switches to stdlib importlib.resources.
src/grid/hirshfeld.py	Switches to stdlib importlib.resources.
src/grid/atomgrid.py	Switches to stdlib importlib.resources.
src/grid/angular.py	Switches to stdlib importlib.resources.
src/grid/init.py	Replaces Flake8 file-level ignore with Ruff equivalent.
doc/installation.rst	Updates dependency/install guidance to reflect pyproject.toml approach.
doc/index.rst	Updates citation text and adds BibTeX entry.
doc/conf.py	Updates Binder link target repo.
README.md	Updates Python badge/CI badge text and citation/install instructions.
LICENSE	Updates license text content.

Comments suppressed due to low confidence (1)

pyproject.toml:97

• [tool.pytest.ini_options] testpaths = ["tests"] doesn't match this repo layout (tests live under src/grid/tests). With this setting, pytest from the repo root is likely to collect 0 tests (and CI may fail or, worse, silently skip). Update testpaths to point at the real test directory (e.g. src/grid/tests) or remove testpaths so default discovery works.

[tool.pytest.ini_options]
minversion = "7.0"
testpaths = ["tests"]
addopts = "-v"

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[PaulWAyers]

Thanks Marco.