install pixi development dependencies

Author: wpbonelli

.github/workflows/mf6.yml

@@ -44,6 +44,10 @@ jobs:
         pixi-version: v0.41.4
         manifest-path: modflow6/pixi.toml
 
+    - name: Install dependencies
+      working-directory: modflow6
+      run: pixi run install
+
     - name: Install FloPy
       working-directory: flopy
       run: |
@@ -119,6 +123,10 @@ jobs:
         pixi-version: v0.41.4
         manifest-path: modflow6/pixi.toml
 
+    - name: Install dependencies
+      working-directory: modflow6
+      run: pixi run install
+
     - name: Install FloPy
       working-directory: flopy
       run: |