Add default values

As per title, we need to ensure that the default are available for the library:

if the user does not specify a componentsMap ensure there is one available that uses the react-diagram default nodes and links.
if the user specify a type that does not exists in the components map, report the error in console but as a fallback use the default type for visualization.

Locate the componentsMap handling and the visualization type lookup in the TypeScript source. Check how react-diagram default nodes and links are exposed, then verify that missing maps use those defaults and unknown types report an error before falling back to the default visualization type.

Written by the indexing model from the issue text.