added attributesToSearchOn

[ahmednfwela]

Pull Request

Related issue

Fixes #336

What does this PR do?

• Adds attributesToSearchOn to SearchQuery and IndexSearchQuery
• Added search_parameter_guide_attributes_to_search_on_1 to code sample
• Added tests

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!

[ahmednfwela]

bors merge

[meili-bors[bot]]

This PR was included in a batch that successfully built, but then failed to merge into main. It will not be retried.

Additional information:

{"message":"At least 1 approving review is required by reviewers with write access.","documentation_url":"https://docs.github.com/articles/about-protected-branches"}

[meili-bors[bot]]

Build succeeded:

• integration-tests (dart 3.0.0)
• linter-check
• pana