Custom generators are not working

**API Platform version(s) affected**: 3.2.20

**Description**
When I'm trying to get the custom generator working, it fails with an error stating that `BaseGenerator` is not exported.

```
Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: Package subpath './lib/generators/BaseGenerator' is not defined by "exports" in /app/generator/node_modules/@api-platform/create-client/package.json imported from /app/generator/Generator.js
at new NodeError (node:internal/errors:405:5)
at exportsNotFound (node:internal/modules/esm/resolve:366:10)
at packageExportsResolve (node:internal/modules/esm/resolve:713:9)
at packageResolve (node:internal/modules/esm/resolve:899:14)
at moduleResolve (node:internal/modules/esm/resolve:973:20)
at defaultResolve (node:internal/modules/esm/resolve:1193:11)
at ModuleLoader.defaultResolve (node:internal/modules/esm/loader:404:12)
at ModuleLoader.resolve (node:internal/modules/esm/loader:373:25)
at ModuleLoader.getModuleJob (node:internal/modules/esm/loader:250:38)
at ModuleWrap. (node:internal/modules/esm/module_job:76:39) {
code: 'ERR_PACKAGE_PATH_NOT_EXPORTED'
}
```

**How to reproduce**
Use the following package.json file:
```json
{
"name": "test-generator",
"version": "1.0.0",
"type": "module",
"dependencies": {
"@api-platform/create-client": "^0.10.0"
}
}
```

Take generator and template from documentation https://api-platform.com/docs/create-client/custom/

Execute:
```console
npm install
npm init @api-platform/client https://demo.api-platform.com/ ../test -- --generator "$(pwd)/Generator.js"
```

**Additional Context**

From what I see in the package.json file at https://github.com/api-platform/create-client/blob/main/package.json#L65, custom generators are tested only inside the `create-client` module.