Add fsspec and s3fs to build.yaml dependencies.

.github/workflows/build.yaml

@@ -64,6 +64,7 @@ jobs:
         run: |
           pip install uv
           uv pip install -r requirements.txt
+          uv pip install fsspec s3fs
 
       # We have two cores so we can speed up the testing with xdist
       - name: Install pytest packages