Extend setup.cfg

Copy metadata and options from pyproject.toml to align installation on
legacy Python/pip/setuptools stacks with the modern pyproject based one.

Signed-off-by: Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>

setup.cfg

@@ -1,3 +1,21 @@
 [metadata]
 name = pyacl
 version = attr: pyacl.__version__
+author = Georg Pfuetzenreuter
+author_email = georg+python@lysergic.dev
+description = High level abstractions over pylibacl
+license = EUPL-1.2
+long_description = file: README.md, LICENSE
+
+[options]
+package_dir=
+    =.
+packages=find:
+python_requires = >=3.6
+
+[options.packages.find]
+exclude=
+    scripts*
+    tests*
+    *.toml
+where=.