Nexus docs with samples for common things like signal, signal-with-start, update, mapping to multiple workflow args

[prasek]

Temporal Affiliation

• [x] I am a Temporal employee

Content Suggestion

Update the Nexus developer guides to includes samples for common Nexus tasks, including the following:

• https://github.com/temporalio/features/issues/664
• https://github.com/temporalio/features/issues/665

@Sushisource suggests we may be able to create a single Nexus example that covers all of these things and then add Nexus dev guide docs using the single example.