include license in build (#630)

Reguired for conda feedstock to work

Author: ianepreston

pyproject.toml

@@ -1,11 +1,12 @@
 [project]
 name = "stats_can"
-version = "3.2.0"
+version = "3.2.1"
 description = "Read StatsCan data into python, mostly pandas dataframes"
 authors = [{ name = "Ian Preston" }]
 requires-python = ">=3.10,<4.0"
 readme = "README.md"
 license = "GPL-3.0-or-later"
+license-files = ["LICENSE"]
 keywords = ["statistics", "Canada", "data", "API"]
 dependencies = ["requests", "tqdm", "pandas", "numpy", "pydantic>=2.9.2"]