add deps to the ci

.github/workflows/ci.yml

@@ -90,7 +90,7 @@ jobs:
           pip install "numpy>=2"
         fi
         pip install -vv .
-        pip install --no-binary=mpi4py mpi4py astropy pytest pytest-cov getdist
+        pip install --no-binary=mpi4py mpi4py astropy pytest pytest-cov getdist derivative numdifftools
 
     - name: Install PocoMC
       if: matrix.python-version != '3.7'