Add benchmark workflow

.github/workflows/benchmarks.yml

@@ -0,0 +1,38 @@
+name: Benchmarks
+
+on:
+  workflow_dispatch:
+  push:
+    branches: ["main"]
+  pull_request:
+    branches: [ "main" ]
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  benchmark:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v5
+
+    - name: Install Rust stable
+      uses: actions-rs/toolchain@v1
+      with:
+        toolchain: stable
+        override: true
+
+    - name: Run benchmarks
+      run: |
+        cd aws_secretsmanager_caching
+        cargo bench --bench benchmark
+
+    - name: Upload benchmark results
+      if: always()
+      uses: actions/upload-artifact@v4
+      with:
+        name: benchmark-results-${{ github.sha }}
+        path: aws_secretsmanager_caching/target/criterion/
+        retention-days: 30