Add ExternalWrapper to dash_component_api

[T4rk1n]

Add new exposed component ExternalWrapper to window.dash_component_api.

It has the props:

• componentPath path to the component in the store. Should use the parent path to create a new path, [...parentPath, "external"]
• componentType string type of the component to hydrate.
• componentNamespace string of the namespace where the component is located. example dash_core_components, dash_table. The namespace must have been loaded before use.
• The rest of the props are given as extra props to the wrapper, allowing the component author to control the props of the component.

Intended usage in libraries to reuse dash components without them being present in the original layout.

[gvwilson]

I'm happy to approve this so that it can be merged but will be doing so on faith - I don't understand the Dash code well enough to do a proper review.

[AnnMarieW]

@T4rk1n

Can you say more about this use case for this?

What if the component is not a simple component but also has components in children or other props?

Is this a replacement for the renderDashComponents function used in dmc?

[T4rk1n]

Is this a replacement for the renderDashComponents function used in dmc?

Yes this is intended for this purpose, rendering components out of the layout tree.