tools: add performance label to benchmark changes

PR-URL: nodejs#47545
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
Reviewed-By: Debadree Chatterjee <debadree333@gmail.com>

Author: anonrig

.github/label-pr-config.yml

@@ -160,7 +160,7 @@ exlusiveLabels:
   /^benchmark\/streams\//: benchmark, stream
   /^benchmark\/([^/]+)\//: benchmark, $1
 
-  /^benchmark\//: benchmark
+  /^benchmark\//: benchmark, performance
 
 allJsSubSystems:
   - assert