Ensure restful_config.yaml gets installed as part of the package

I'm not quite sure why this was reverted in !676 (merged), but here it is again.

cc @schmidtp @roscar

setup.py

@@ -120,6 +120,7 @@ setup(
     packages=find_packages("src"),
     package_dir={"": "src"},
     package_data={
+        "cal_tools": ["restful_config.yaml"],
         "xfel_calibrate": [
             "bin/*.sh",
             "titlepage.tmpl",