TO FIXUP: add readme

Author: GuillaumeLagrange

packages/playwright/README.md

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+<div align="center">
+<h1><code>@codspeed/playwright</code></h1>
+
+[Playwright](https://playwright.dev) integration for [CodSpeed](https://codspeed.io), to benchmark [Electron](https://www.electronjs.org) apps end-to-end
+
+[![CI](https://github.com/CodSpeedHQ/codspeed-node/actions/workflows/ci.yml/badge.svg)](https://github.com/CodSpeedHQ/codspeed-node/actions/workflows/ci.yml)
+[![npm (scoped)](https://img.shields.io/npm/v/@codspeed/playwright)](https://www.npmjs.com/package/@codspeed/playwright)
+[![Discord](https://img.shields.io/badge/chat%20on-discord-7289da.svg)](https://discord.com/invite/MxpaCfKSqF)
+[![CodSpeed Badge](https://img.shields.io/endpoint?url=https://codspeed.io/badge.json)](https://codspeed.io/CodSpeedHQ/codspeed-node)
+
+</div>
+
+## Documentation
+
+Check out the [documentation](https://docs.codspeed.io/benchmarks/nodejs) for complete integration instructions.
+
+## Installation
+
+Install the plugin [`@codspeed/playwright`](https://www.npmjs.com/package/@codspeed/playwright) alongside `playwright` and your `electron` app dependency:
+
+```sh
+npm install --save-dev @codspeed/playwright playwright electron
+```
+
+or with `yarn`:
+
+```sh
+yarn add --dev @codspeed/playwright playwright electron
+```
+
+or with `pnpm`:
+
+```sh
+pnpm add --save-dev @codspeed/playwright playwright electron
+```
+
+## Usage
+
+This integration measures an Electron app driven through Playwright. Build your
+app first so the Electron main entrypoint exists (e.g. `out/main/index.js`),
+then write a benchmark with the `bench` function.
+
+`bench` launches the app once per round, drives it through the provided
+function, and reports the time spent inside that function to CodSpeed:
+
+```ts title="bench/inbox.bench.ts"
+import { bench } from "@codspeed/playwright";
+import path from "node:path";
+
+bench(
+  "inbox-search",
+  async ({ page }) => {
+    await page.fill("#search", "quarterly report");
+    await page.waitForSelector("#results");
+  },
+  {
+    appPath: path.resolve("out/main/index.js"),
+    // Bring the app to a steady state before each measured round (not measured).
+    setup: async ({ page }) => {
+      await page.waitForSelector("#main:not(.loading)");
+    },
+    rounds: 5,
+  },
+);
+```
+
+### Options
+
+| Option                   | Type                                  | Default             | Description                                                                               |
+| ------------------------ | ------------------------------------- | ------------------- | ----------------------------------------------------------------------------------------- |
+| `appPath`                | `string`                              | _(required)_        | Absolute path to the Electron main entrypoint (e.g. `out/main/index.js`).                 |
+| `rounds`                 | `number`                              | `1`                 | Number of measurement rounds. Overridable via the `CODSPEED_ROUNDS` environment variable. |
+| `electronArgs`           | `string[]`                            | `[]`                | Extra CLI flags forwarded to Electron.                                                    |
+| `cwd`                    | `string`                              | `process.cwd()`     | Working directory for the Electron process. Also where `electron` is resolved from.       |
+| `electronExecutablePath` | `string`                              | resolved `electron` | Absolute path to the Electron binary. Set only to override the default resolution.        |
+| `setup`                  | `({ page }) => void \| Promise<void>` | —                   | Runs before each round, after the window opens. Not measured.                             |
+| `teardown`               | `({ page }) => void \| Promise<void>` | —                   | Runs after each round, before the app closes. Not measured.                               |
+
+The function receives a Playwright [`Page`](https://playwright.dev/docs/api/class-page) for the Electron window as `page`.
+
+## Running the benchmarks
+
+Run your benchmark file with Node (or `tsx` for TypeScript):
+
+```bash
+$ node bench/inbox.bench.ts
+[CodSpeed] [round 1/5] 42.13 ms
+...
+```
+
+Locally this simply runs the app and prints per-round timings. Instrumentation
+and uploads to CodSpeed only happen in the
+[CI environment](https://docs.codspeed.io/benchmarks/nodejs#running-the-benchmarks-in-your-ci),
+where the CodSpeed runner picks up the results.