Function register

register(
provider: StorefrontProvider,
options?: StorefrontRegisterOptions,
): Promise<StorefrontRegistration>
Registers a Storefront VPW integrator.

Creates the VPW channel (if needed), launches the browser-zone Storefront window hidden, then adds the provider to the in-process registry.
Parameters
- provider: StorefrontProvider
  Storefront integrator implementation.
- options: StorefrontRegisterOptions = {}
  Optional launch options for the VPW window.
Returns Promise<StorefrontRegistration>
Registration metadata and an updateAppCardButtons helper.
Remarks
Call from the provider process (the platform/provider window), not from arbitrary content views. The channel and host singleton are bound to the caller's fin.me.identity — same constraint as legacy Storefront.register().

Throws
Error if provider.icon is missing.

Throws
StorefrontVpwProviderAlreadyRegisteredError if a provider with the same id is already registered.
Example
```
import { Storefront, type StorefrontProvider } from '@openfin/workspace-platform';

const provider: StorefrontProvider = {
    id: 'my-store',
    title: 'My Store',
    icon: 'https://example.com/icon.png',
    getApps: async () => [],
    getNavigation: async () => [],
    getLandingPage: async () => undefined,
    getFooter: async () => ({ logo: { src: '' } }),
    launchApp: async () => undefined
};

await Storefront.register(provider);
await Storefront.show();
```