Add custom nodes conventions and patterns guide

[junminahn]

Summary

Adds a new documentation guide for the community-nodes package that captures the conventions and patterns used across custom n8n nodes.

What’s included

• Repository layout for custom nodes, credentials, tests, icons, and build output
• Package-level conventions for community-nodes metadata, tooling, dependency policy, and scripts
• Node and credential file naming conventions and description shape guidance
• Shared helper patterns for reusable node logic
• Execution, webhook, HTTP request, environment configuration, and error-handling conventions
• TypeScript, lint, and testing guidance specific to the package
• Documentation structure and style expectations for node docs
• A checklist for adding new nodes
• A reference table of existing nodes and their associated styles/credentials

Impact

This change is documentation-only and does not affect runtime behavior. It provides a single source of truth for contributors adding or reviewing custom nodes in the repository.

Files changed

• docs/community-nodes/conventions-and-patterns.md

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[ratheesh-aot]

LGTM