Docs: Enhance API Documentation with JSON:API Guide, Polling vs Webhooks, and Core Examples

[dodeja]

This PR enhances the Terminal49 API documentation with several key improvements:

New Guides

• Created comprehensive JSON:API guide explaining the format used by Terminal49's API
• Added detailed Polling vs. Webhooks comparison guide with implementation examples
• Started Webhooks implementation guide (in progress)

Updated Core Documentation

• Enhanced Getting Started guide with clearer introduction and setup instructions
• Improved Capabilities Overview to highlight Terminal49's API features
• Updated Tracking Request documentation with detailed examples and troubleshooting

Documentation Structure

• Organized all guides within the /docs folder following Mintlify standards
• Updated Documentation Improvement Tracker to reflect progress and future plans

These changes aim to make Terminal49's API more approachable for new developers while providing in-depth resources for advanced integration scenarios.

[graphite-app]

The documentation references a "Tracking Request Lifecycle" guide that doesn't appear to exist yet based on the Documentation Improvement Tracker. This creates a broken link for users. Consider either:

1. Creating the referenced guide as part of this PR
2. Updating this reference to point to existing documentation
3. Adding a note that this guide is coming soon

Broken documentation links can frustrate users trying to find complete information about failure reasons.

Suggested change

	<Note>
	See the [Tracking Request Lifecycle](/api-docs/in-depth-guides/tracking-request-lifecycle) guide for a complete list of failure reasons.
	</Note>
	<Note>
	For information about possible failure reasons, see our [Error Handling documentation](/api-docs/guides/error-handling).
	</Note>

Spotted by Diamond

Is this helpful? React 👍 or 👎 to let us know.