Usability and interoperability

• C# interop example
• Improve API usability
• Add better Nostra.Client (still WIP)
• Nip40 (Expiration Timestamp)
• Nip01 - Add metadata note
• Nip44 (Encrypted payloads)
• Nip19 (Shareable entities)
• Improve error handling according to NIP 20
• Nip01 - Add Parameterized events
• Nip01 - Add replaceable events
• Ephemeral notes