Add support for similar docs query

[JiaYingZhang]

Pull Request

Related issue

Fixes #646

What does this PR do?

• Add support for similar docs queries with v1.13 version api #646. It works for my project.
• Completed but commented on the test cases; I will finish the remaining parts after the PR #554 is merged.

PR checklist

Please check if your PR fulfills the following requirements:

• [x] Does this PR fix an existing issue, or have you listed the changes applied in the PR description (and why they are needed)?
• [x] Have you read the contributing guidelines?
• [x] Have you made sure that the title is accurate and descriptive of the changes?

Thank you so much for contributing to Meilisearch!

Summary by CodeRabbit

• New Features

  • Introduced similarity search capabilities to find documents similar to a specified one within an index.
  • Added configurable options for similarity queries, including pagination, filtering, attribute selection, and detailed ranking score information in results.

• Documentation

  • Included example usage and detailed documentation for the similarity search functionality.