impossible to generate a patch

I'm following the documentation but it doesn't work
```
vim node_modules/playwright/lib/utils/registry.js # add the missing freebsd bits

npx patch-package playwright
patch-package 6.1.2
• Creating temporary folder
• Installing playwright@1.10.0 with yarn
warning package.json: No license field
warning No license field
error /tmp/tmp-13383BSkdsxgKH7EA/node_modules/playwright: Command failed.
Exit code: 1
Command: node install.js
Arguments:
Directory: /tmp/tmp-13383BSkdsxgKH7EA/node_modules/playwright
Output:
/tmp/tmp-13383BSkdsxgKH7EA/node_modules/playwright/lib/utils/registry.js:190
throw new Error('Unsupported platform: ' + process.platform);
```

Why?