Add project metadata to pyproject.toml

So that meson-python has something to to generate the project
metadata.

Also sync the meson-python generated metadata (minus the README) to
PKG-INFO.in which is used when meson is used standalone.

PKG-INFO.in

@@ -1,16 +1,9 @@
-Metadata-Version: 1.2
+Metadata-Version: 2.1
 Name: pycairo
 Version: @VERSION@
 Summary: Python interface for cairo
-Home-page: https://pycairo.readthedocs.io
-Maintainer: Christoph Reiter
-Maintainer-email: reiter.christoph@gmail.com
-License: UNKNOWN
-Description: Pycairo is a Python module providing bindings for the cairo graphics library
-Platform: UNKNOWN
-Classifier: Operating System :: OS Independent
-Classifier: Programming Language :: Python :: 3
-Classifier: Programming Language :: Python :: Implementation :: CPython
-Classifier: Programming Language :: Python :: Implementation :: PyPy
-Classifier: License :: OSI Approved :: GNU Lesser General Public License v2 (LGPLv2)
-Classifier: License :: OSI Approved :: Mozilla Public License 1.1 (MPL 1.1)
+Maintainer-Email: Christoph Reiter <reiter.christoph@gmail.com>
+License: LGPL-2.1-only OR MPL-1.1
+Project-URL: Homepage, https://pycairo.readthedocs.io
+Project-URL: Source, https://github.com/pygobject/pycairo
+Requires-Python: >=3.9

pyproject.toml

@@ -1,3 +1,13 @@
+[project]
+name = "pycairo"
+version = "1.26.2"
+description = "Python interface for cairo"
+readme = "README.rst"
+requires-python = ">=3.9"
+license = {text = "LGPL-2.1-only OR MPL-1.1"}
+maintainers = [{name = "Christoph Reiter", email = "reiter.christoph@gmail.com"}]
+urls = {Homepage = "https://pycairo.readthedocs.io", Source = "https://github.com/pygobject/pycairo"}
+
 [tool.poetry]
 name = "pycairo"
 version = "1.26.2"