Update license information in pyproject.toml: set license type and include license files

Author: PierreRaybaut

pyproject.toml

@@ -9,13 +9,13 @@ name = "PlotPy"
 authors = [{ name = "Codra", email = "p.raybaut@codra.fr" }]
 description = "Curve and image plotting tools for Python/Qt applications"
 readme = "README.md"
-license = { file = "LICENSE" }
+license = "BSD-3-Clause"
+license-files = ["LICENSE"]
 classifiers = [
     "Development Status :: 5 - Production/Stable",
     "Intended Audience :: Developers",
     "Intended Audience :: Education",
     "Intended Audience :: Science/Research",
-    "License :: OSI Approved :: BSD License",
     "Operating System :: MacOS :: MacOS X",
     "Operating System :: Microsoft :: Windows :: Windows 7",
     "Operating System :: Microsoft :: Windows :: Windows 8",