Add missing deps to test workflow

Author: AndrewSazonov

.github/workflows/test.yml

@@ -199,11 +199,14 @@ jobs:
             pixi init easydiffraction_py$py_ver
             cd easydiffraction_py$py_ver
 
+            echo "Setting macOS 14.0 as minimum required"
+            pixi project system-requirements add macos 14.0
+
             echo "Adding Python $py_ver"
             pixi add "python=$py_ver"
 
-            echo "Setting macOS 14.0 as minimum required"
-            pixi project system-requirements add macos 14.0
+            echo "Adding GNU Scientific Library (GSL)"
+            pixi add gsl
 
             echo "Looking for wheel in ../dist/py$py_ver/"
             ls -l "../dist/py$py_ver/"