feat: Add nix setup to testing workflow

.github/actions/setup-nix/action.yml

@@ -0,0 +1,23 @@
+name: Setup Nix
+description: Sets up nix for running tests with devimint
+
+runs:
+  using: 'composite'
+  steps:
+    - name: Install Nix
+      uses: cachix/install-nix-action@V27
+      with:
+        nix_path: nixpkgs=channel:nixos-23.11
+        extra_nix_config: |
+          connect-timeout = 15
+          stalled-download-timeout = 15
+
+    # - name: Setup Cachix
+    #   uses: cachix/cachix-action@v15
+    #   with:
+    #     name: fedimint
+    #     authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+    #   continue-on-error: true
+
+    - name: Run nix develop
+      run: nix develop

.github/workflows/verify.yml

@@ -63,6 +63,9 @@ jobs:
       - name: Install dependencies
         uses: ./.github/actions/install-deps
 
+      - name: Setup Nix
+        uses: ./.github/actions/setup-nix
+
       - name: Setup Playwright
         run: pnpm exec playwright install