Enable dependency caching on e2e GHA

.github/workflows/cypress.yml

@@ -19,7 +19,8 @@ jobs:
         uses: actions/setup-node@v2
         with:
           node-version: 16.10.0
-      - run: npm install
+          cache: 'npm'
+          cache-dependency-path: frontend/package-lock.json
       - name: ${{ matrix.browser }} browser tests (Mempool)
         uses: cypress-io/github-action@v2
         with: