build: include py.typed in package-data for typed package publishing

Author: nimaxin

sdk/python/packages/flet/pyproject.toml

@@ -101,3 +101,9 @@ build-backend = "setuptools.build_meta"
 
 [tool.uv.sources]
 mkdocs-external-images = { git = "https://github.com/flet-dev/mkdocs-external-images", tag = "v0.2.0" }
+
+[tool.setuptools.packages.find]
+where = "src"
+
+[tool.setuptools.package-data]
+"flet" = ["py.typed"]