Ditch setup.cfg and replace it with pyproject.toml

Move flake8 configuration to its own `.flake8` file.

.flake8

@@ -0,0 +1,40 @@
+# Configure flake8
+
+[flake8]
+max-line-length = 88
+max-doc-length = 79
+ignore =
+    # Too many leading '#' for block comment
+    E266,
+    # Line too long (82 > 79 characters)
+    E501,
+    # Do not use variables named 'I', 'O', or 'l'
+    E741,
+    # Line break before binary operator (conflicts with black)
+    W503,
+    # Functions too long. The kernels will end up a bit long but not complex.
+    CFQ001,
+    # Number of arguments. Kernels take only scalars (no lists or arrays)
+    CFQ002,
+exclude =
+    .git,
+    __pycache__,
+    .ipynb_checkpoints,
+    doc/_build,
+per-file-ignores =
+    # disable unused-imports errors on __init__.py
+    __init__.py: F401
+    # disable unused arguments in kernel files
+    _kernels.py: U100
+
+# Configure flake8-rst-docstrings
+# -------------------------------
+# Add some roles used in our docstrings
+rst-roles =
+    class,
+    func,
+    mod,
+    meth,
+    ref,
+# Ignore "Unknown target name" raised on citations
+extend-ignore = RST306

pyproject.toml

@@ -1,7 +1,45 @@
-# Specify that we use setuptools and setuptools_scm (to generate the version
-# string). Actual configuration is in setup.cfg.
+[project]
+name = "choclo"
+description = "Kernel functions for your geophysical models"
+dynamic = ["version"]
+authors = [
+  {name="The Choclo Developers", email="[email protected]"},
+]
+maintainers = [
+  {name = "Santiago Soler", email = "[email protected]"}
+]
+readme = "README.md"
+license = {text = "BSD-3-Clause"}
+keywords = ["geoscience", "geophysics"]
+classifiers = [
+    "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",
+    "Programming Language :: Python :: 3",
+    "Topic :: Scientific/Engineering",
+    "Topic :: Software Development :: Libraries",
+]
+requires-python = ">=3.7"
+dependencies = [
+    "numpy>=1.19",
+    "numba>=0.52",
+]
+
+[project.urls]
+"Homepage" = "https://www.fatiando.org/choclo"
+"Documentation" = "https://www.fatiando.org/choclo"
+"Repository" = "https://github.com/fatiando/choclo.git"
+"Changelog" = "https://www.fatiando.org/choclo/latest/changes.html"
+"Bug Tracker" = "https://github.com/fatiando/choclo/issues"
+"Source Code" = "https://github.com/fatiando/choclo"
+"Release Notes" = "https://github.com/fatiando/choclo/releases"
+
 [build-system]
-requires = ["setuptools>=45", "wheel", "setuptools_scm[toml]>=6.2"]
+requires = ["setuptools>=61", "wheel", "setuptools_scm[toml]>=8.0.3"]
 build-backend = "setuptools.build_meta"
 
 [tool.setuptools_scm]