Extend list of PyPI classifiers in pyproject.toml (#480)

Extend the list of classifiers, mostly restore the ones that were lost
during the move from `setup.cfg` to `pyproject.toml`.

pyproject.toml

@@ -12,9 +12,20 @@ readme = "README.md"
 license = {text = "BSD-3-Clause"}
 keywords = ["geoscience", "geophysics"]
 classifiers = [
- "Programming Language :: Python :: 3",
+ "Development Status :: 5 - Production/Stable",
+ "Intended Audience :: Science/Research",
+ "Intended Audience :: Developers",
+ "Intended Audience :: Education",
  "License :: OSI Approved :: BSD License",
+ "Natural Language :: English",
  "Operating System :: OS Independent",
+ "Topic :: Scientific/Engineering",
+ "Topic :: Software Development :: Libraries",
+ "Programming Language :: Python :: 3 :: Only",
+ "Programming Language :: Python :: 3.8",
+ "Programming Language :: Python :: 3.9",
+ "Programming Language :: Python :: 3.10",
+ "Programming Language :: Python :: 3.11",
 ]
 requires-python = ">=3.8"
 dependencies = [