docs(carousel): add docs for carousel

[chintankavathia]

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Documentation.
Examples.
Dashboards Demo.
Playwright report.

Coverage Reports:

• charts-ng
• dashboards-ng
• element-ng
• element-translate-ng
• maps-ng
• native-charts-ng

[gemini-code-assist]

Code Review

This pull request introduces documentation and entry point exports for the new Carousel component. It adds a new documentation page detailing the usage, design, and code examples for si-carousel, registers the page in the components index and mkdocs.yml navigation, and exports the component in projects/element-ng/docs.ts. I have no feedback to provide as there are no review comments or issues identified in these changes.

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