Add label when PR gets reassigned (#34866)

Author: damccorm

scripts/ci/pr-bot/findPrsNeedingAttention.ts

@@ -176,6 +176,12 @@ async function processPull(
         issue_number: pull.number,
         name: SLOW_REVIEW_LABEL,
       });
+      await client.rest.issues.addLabels({
+        owner: REPO_OWNER,
+        repo: REPO,
+        issue_number: pull.number,
+        labels: ["reassigned-reviewers"],
+      });
     }
 
     return;