fix: adding numpy and cython to sdist

Author: Lachlan Grose

.github/workflows/release-please.yml

@@ -157,7 +157,9 @@ jobs:
     - uses: actions/checkout@v3
 
     - name: Build SDist
-      run: pipx run build --sdist
+      run: |
+        pip install numpy cython
+        pipx run build --sdist
 
     - uses: actions/upload-artifact@v3
       with: