Version 0.2.0

This release focuses on stronger typed graph specs, better node-view handling,
and improved docs and packaging.

Highlights

• NodeSpec view support — added a view parameter to NodeSpec and
  fixed add_node behavior so embedded views are preserved when adding nodes
  programmatically.
• Safer embedded view handling — fixed an AttributeError when node views
  are Panel Viewer objects or other arbitrary view-like objects.
• EdgeSpec handle targeting — added sourceHandle and targetHandle
  fields to support explicit edge-to-port connections.
• Spec auto-serialization — added automatic serialization for NodeSpec
  and EdgeSpec objects to reduce boilerplate when using dataclass-based graph
  definitions.
• Handle rendering fix — corrected empty handle list behavior so [] is
  treated distinctly from missing/undefined handles.
• Styling hook for labels — added the rf-node-label CSS class on node
  labels for easier targeted styling.
• Docs and onboarding updates — quickstart and index docs now explicitly
  document the required pn.extension("jsoneditor") setup; additional how-to
  docs were updated for new handle and serialization behavior.
• Packaging reliability — ensured the frontend dist assets are included
  in distributions.