Re-add project URLs after migration to pyproject.toml (#1986)

Following spec:
https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#urls

Author: Jamie-

pyproject.toml

@@ -25,6 +25,10 @@ dependencies = [
     "wcwidth",
 ]
 
+[project.urls]
+Homepage = "https://github.com/prompt-toolkit/python-prompt-toolkit"
+Documentation = "https://python-prompt-toolkit.readthedocs.io/en/stable/"
+
 [tool.ruff]
 target-version = "py37"
 lint.select = [