pyproject.toml: add metadata

pyproject.toml

@@ -3,6 +3,22 @@ name = "cadquery"
 version = "2.1"
 description = "A python parametric CAD scripting framework based on OCCT"
 authors = [ "Parametric Products Intellectual Holdings, LLC" ]
+license = "Apache-2.0"
+readme = "README.md"
+homepage = "https://cadquery.readthedocs.io/en/latest/"
+repository = "https://github.com/CadQuery/cadquery"
+documentation = "https://cadquery.readthedocs.io/en/latest/"
+keywords = ["modeling", "cad", "stl", "opencascade", "brep"]
+classifiers = [
+    "Development Status :: 5 - Production/Stable",
+    "Intended Audience :: Developers",
+    "Intended Audience :: Science/Research",
+    "Operating System :: POSIX",
+    "Operating System :: MacOS",
+    "Operating System :: Unix",
+    "Topic :: Software Development :: Libraries :: Python Modules",
+    "Topic :: Scientific/Engineering"
+]
 
 [tool.poetry.dependencies]
 python = "^3.8"