Multiple providers can be registered. In that case, providers are asked in
parallel and the results are merged. A failing provider (rejected promise or exception) will
not cause a failure of the whole operation.
Parameters
scheme: string|string[]
A scheme or schemes that defines which documents this provider is applicable to. Can be * to target all documents.
Register a timeline provider.
Multiple providers can be registered. In that case, providers are asked in parallel and the results are merged. A failing provider (rejected promise or exception) will not cause a failure of the whole operation.