feat: add CodSpeed performance monitoring

- Downgrade vitest from v4 to v3.2.4 for CodSpeed compatibility
- Add @codspeed/vitest-plugin for performance instrumentation
- Configure vitest with CodSpeed plugin
- Add GitHub Actions workflow for automated benchmarks
- Add CodSpeed badge to README

Author: CodSpeed Bot

.github/workflows/codspeed.yml

@@ -0,0 +1,37 @@
+name: CodSpeed
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  id-token: write
+
+jobs:
+  benchmarks:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: pnpm/action-setup@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: pnpm
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      - name: Build project
+        run: pnpm run build
+
+      - name: Run benchmarks
+        uses: CodSpeedHQ/action@v4
+        with:
+          mode: simulation
+          run: pnpm -F bench run bench

README.md

@@ -5,6 +5,7 @@
 [![npm version][npm-version-src]][npm-version-href]
 [![bundle][bundle-src]][bundle-href]
 [![License][license-src]][license-href]
+[![CodSpeed][codspeed-src]][codspeed-href]
 
 A TypeScript rewrite of [markdown-it](https://github.com/markdown-it/markdown-it) with first-class typings, modern tooling, and enhancements.
 
@@ -122,3 +123,5 @@ This project owes its foundation to the [markdown-it](https://github.com/markdow
 [bundle-href]: https://bundlephobia.com/result?p=markdown-exit
 [license-src]: https://img.shields.io/github/license/serkodev/markdown-exit.svg?style=flat&colorA=00AF6B&colorB=000
 [license-href]: https://github.com/serkodev/markdown-exit/blob/main/LICENSE
+[codspeed-src]: https://img.shields.io/badge/CodSpeed-Performance-00AF6B?style=flat&colorB=000
+[codspeed-href]: https://codspeed.io/serkodev/markdown-exit?utm_source=badge

package.json

@@ -20,6 +20,7 @@
   },
   "devDependencies": {
     "@antfu/eslint-config": "catalog:",
+    "@codspeed/vitest-plugin": "catalog:tests",
     "@types/node": "catalog:types",
     "bumpp": "catalog:",
     "eslint": "catalog:",

packages/bench/package.json

@@ -6,6 +6,7 @@
     "bench": "vitest bench"
   },
   "devDependencies": {
+    "@codspeed/vitest-plugin": "catalog:tests",
     "@types/commonmark": "catalog:bench",
     "@types/markdown-it": "catalog:bench",
     "commonmark": "catalog:bench",