add benchmark repro details

Author: overlookmotel

src/blog/2025-10-09-oxlint-js-plugins.md

@@ -231,6 +231,27 @@ Oxlint vs ESLint linting a medium-sized TypeScript project [vuejs/core](https://
 | Oxlint                       | 582 ms   |
 | Oxlint with custom JS plugin | 584 ms   |
 
+<div>
+<details>
+<summary>Details</summary>
+
+- Benchmark repo: https://github.com/camc314/core/tree/c/bench-custom-plugins
+- Benchmarked on 2023 MacBook Pro M2 Max
+- Bench command:
+
+```sh
+hyperfine \
+  --warmup 1 \
+  --runs 5 \
+  'pnpm run oxlint' \
+  'pnpm run oxlint-with-custom-plugin' \
+  'pnpm run eslint-with-custom-plugin' \
+  'pnpm run eslint-with-custom-plugin-parallel' -i
+```
+
+</details>
+</div>
+
 In this example, the cost of adding a simple JS plugin to Oxlint is less than 1%, and Oxlint is 8x faster than ESLint,
 even using ESLint's new multi-threaded runner.