Support for async plugins

[JonasKruckenberg]

I have this use case in my project where I have a dependency that relies on wasm and must therefore make use of promises.
My current solution consists of two parts, first I return the SlatePlugin as a promise

function createDemoPlugin = async (): Promise<SlatePlugin> => {...}

and then wrap the SlatePlugin instance inside a react Suspense element

export const AsyncSlatePlugins = <T extends SPEditor = SPEditor>({
    children,
    plugins,
    ...options
  }: SlatePluginsProps<T>) => {
    
    const SlatePlugins = lazy(async () => {
        // This allows promises and plain objects
        const resolvedPlugins = await Promise.all(plugins || [])

        return {
            // it's weird I know
            default: () => <SlatePlugins {...options} plugins={resolvedPlugins}>{children}</SlatePlugins>
        }
    })
    
    return <Suspense fallback={children}>
        <SlatePlugins />
    </Suspense>
  }

Optimally there would be async support on a per-hook basis but this addresses quite a lot of pain points already.
What do you think?

[zbeyens]

This looks good to me. I don't have any async use-case in mind so we can just extend the hooks on demand.