Release 8.1.0

New features and improvements

• Made CachedTypeInspector thread safe #386
  Previously, using an instance of Serializer or Deserializer was not thread-safe,
  although the intention was for them to be thread safe. The only mutable state is
  inside CachedTypeInspector and was not properly protected against concurrent mutation.

Other fixes

• Fix type conflicts when targeting frameworks without nullability attributes #460