Add explicit installation of Rollup helper in E2E test workflow

Author: Lukecsharpwalker

.github/workflows/e2e-tests.yml

@@ -14,6 +14,9 @@ jobs:
       cancel-in-progress: true
 
     steps:
+      - name: Install Rollup helper explicitly
+        run: npm install --no-save --omit=dev @rollup/rollup-linux-x64-gnu@$(node -p "require('./package.json').devDependencies.rollup || '4'")
+
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
         with: { node-version: 20, cache: npm }