docs: improve developer guide for pnpm and windows

Improves the developer guide for pnpm and Windows.

See for the Windows change:
angular#29705.

Author: devversion

docs/DEVELOPER.md

@@ -5,10 +5,13 @@
 To get started locally, follow these instructions:
 
 1. If you haven't done it already, [make a fork of this repo](https://github.com/angular/angular-cli/fork).
-1. Clone to your local computer using `git`.
-1. Make sure that you have Node `v18.19` or higher installed. See instructions [here](https://nodejs.org/en/download/).
-1. Make sure that you have `yarn` installed; see instructions [here](https://yarnpkg.com/lang/en/docs/install/).
-1. Run `yarn` (no arguments) from the root of your clone of this project to install dependencies.
+2. If you are on Windows, see [the extra steps needed for contributing on Windows](#windows)
+3. Clone to your local computer using `git`.
+4. Make sure that you have Node `v20.18.1` or higher installed. See instructions [here](https://nodejs.org/en/download/).
+5. Install `pnpm`.
+   - You can install pnpm by running `npm i -g pnpm@9`.
+   - See detailed instructions [here](https://pnpm.io/installation).
+6. Run `pnpm install` from the root of your clone of this project to install dependencies.
 
 ## Building and Installing the CLI
 
@@ -170,3 +173,17 @@ Adding a package to this repository means running two separate commands:
 
 For private packages, you will need to add a `"private": true` key to your package.json manually.
 This will require re-running the template admin script.
+
+## Windows
+
+To contribute to Angular using a Windows machine, you need to use the [Windows Linux Subsystem](https://learn.microsoft.com/en-us/windows/wsl/about) (also known as WSL).
+Installing WSL on your machine requires a few extra steps, but we believe it's generally useful for developing on Windows:
+
+1.  Run `wsl --install` from Powershell (as administrator).
+2.  Restart your machine.
+3.  Enter the WSL environment by running: `wsl`.
+4.  Continue with the developer guide as if you were on a native Linux system.
+
+For a more detailed guide, refer to the official Microsoft documentation: [Installing WSL](https://learn.microsoft.com/en-us/windows/wsl/install).
+
+**Note:** Angular continues to support native Windows development via the `ng` CLI and rigorously tests on Windows for every code change. This recommendation specifically applies to contributing to the Angular codebase itself.