how can i use when => Promise<boolean>

[FunctionRun]

"react-router-navigation-prompt": "^1.8.6",

Do you want to request a feature or report a bug? feature

What is the current behavior?

<NavigationPrompt
    when={true}
/>

What is the expected behavior?

<NavigationPrompt
    when={async () => {
        const flag:boolean = await xxxxxx();
        return flag
    }}
/>

[ZacharyRSmith]

This is not currently supported. Please open a PR if you get it working!