Bundle hub registration schema in the installed package

Load the schema from reuse_surface/hub/ next to store.py and declare
package-data so pip install includes the YAML in site-packages. Fixes
hub register 500 in the container image.

pyproject.toml

@@ -26,4 +26,7 @@ reuse-surface = "reuse_surface.cli:main"
 
 [tool.setuptools.packages.find]
 where = ["."]
-include = ["reuse_surface*"]
+include = ["reuse_surface*"]
+
+[tool.setuptools.package-data]
+reuse_surface = ["hub/hub-registration.schema.yaml"]