chore: ensure benchmark runs on node v15

Author: ColinEberhardt

.github/workflows/benchmark.yml

@@ -10,7 +10,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
-      - uses: actions/setup-node@v1
+      - name: Setup Node.js
+        uses: actions/setup-node@v1
+        with:
+          node-version: 15
       - run: npm ci
       - run: npm run asbuild:untouched
       # Run benchmark with `go test -bench` and stores the output to a file