docs: n8n cheatsheet

[Pragnesh-10]

What does this PR do?

This PR adds a new, comprehensive cheat sheet for n8n (the open-source workflow automation tool) to the toolkit section.

What is included in the new cheat sheet?

• Getting Started: Quick start commands for npm, Docker, and Docker Compose.
• Core Concepts: Definitions of Workflows, Nodes, Items, and Connections.
• Expressions & Variables: Syntax basics, referencing other nodes, and built-in global variables ($execution, $today, etc.).
• Core Nodes & Triggers: Detailed references for the HTTP Request, IF, Switch, Set, and Merge nodes, plus cron-patterns for triggers.
• Code Node: Common snippets for Run Once per Item, Run Once for All Items, and grouping/flattening logic.
• Advanced Workflows: Coverage of Sub-Workflows, Community Nodes, and Pagination built-ins.
• Error Handling: Node-level continuing strategies and dedicated Error Workflows.
• CLI & Keyboard Shortcuts: The most useful terminal commands and canvas shortcuts.

Motivation

As the popularity of low-code/no-code platforms and API orchestrations grows, n8n has become a daily driver for many developers. Having a quick reference for n8n's syntax, built-ins, and expressions will be a huge time-saver for the community.

Validation

• Formatted correctly with the project's standard markdown and magic syntax variants.
• Tested locally using the Hexo dev server to ensure components and columns ({.cols-2}, {.col-span-2}, etc.) render perfectly.

[Pragnesh-10]

can you review it and suggest me any changes if required