chat-sample is not Windows friendly

[alexr00]

npm install fails:

PS C:\Users\alros\repos\Microsoft\vscode-extension-samples\chat-sample> npm install

> chat-sample@0.1.0 postinstall
> npm run setupTiktoken


> chat-sample@0.1.0 setupTiktoken
> cp node_modules/@vscode/prompt-tsx/dist/base/tokenizer/cl100k_base.tiktoken out/

'cp' is not recognized as an internal or external command,
operable program or batch file.
npm ERR! code 1
npm ERR! path C:\Users\alros\repos\Microsoft\vscode-extension-samples\chat-sample
npm ERR! command failed
npm ERR! command C:\Windows\system32\cmd.exe /d /s /c npm run setupTiktoken

npm ERR! A complete log of this run can be found in: C:\Users\alros\AppData\Local\npm-cache\_logs\2024-05-30T13_14_26_042Z-debug-0.log
PS C:\Users\alros\repos\Microsoft\vscode-extension-samples\chat-sample>