Context

Currently "Type registries cannot be modified after instantiation." This leads to a situation where if we want to provide an additional codec for an operation, as in pymongoarrow.api.write, we have to discard the TypeRegistry given by the user. We can add an API to extend the type registry to avoid this constraint.

Definition of done

Add an API to modify a TypeRegistry to add codecs. We don't yet have a need to remove codecs.

Pitfalls

None