Pin the build backend so sdist filenames stay PEP 625 compliant

pyproject.toml

@@ -0,0 +1,14 @@
+# Declaring the build backend makes builds reproducible: `python -m build` resolves these
+# requirements in an isolated environment instead of using whatever setuptools happens to be
+# first on PATH.
+#
+# The version floor is not arbitrary. setuptools 69.3 is where sdist filenames became
+# PEP 625 normalised ("python_dwca_reader-X.Y.Z.tar.gz" rather than "python-dwca-reader-..."),
+# and PyPI now rejects the old form outright. Building 0.17.0 with an older setuptools
+# produced an sdist the upload refused.
+#
+# Package metadata deliberately stays in setup.py for now; this file only pins how the build
+# happens, not what is built.
+[build-system]
+requires = ["setuptools>=69.3", "wheel"]
+build-backend = "setuptools.build_meta"

setup.py

@@ -12,6 +12,7 @@
     license="BSD licence, see LICENCE.txt",
     description="A simple Python package to read Darwin Core Archive (DwC-A) files.",
     long_description=open("README.rst").read(),
+    long_description_content_type="text/x-rst",
     python_requires=">=3.8",
     classifiers=[
         "Programming Language :: Python :: 3",