Implement the proximity precision option

[KatsukiFujimoto]

Pull Request

Related issue

N/A

What does this PR do?

• Implements the proximity precision option so that you can set it through a model file.
  • This option can be useful when you prefer shorter indexing time to higher search precision.
  • https://www.meilisearch.com/docs/reference/api/settings#proximity-precision
• Adds sample code for it in README.

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?

[brunoocasali]

Can you rebase your code now?!

[KatsukiFujimoto]

Thank you for fixing the issue. I rebased this branch.

[ellnix]

bors merge

[meili-bors[bot]]

Build succeeded:

• integration-tests (Rails 6.1 with Ruby 2.7)
• integration-tests (Rails 6.1 with Ruby 3.0)
• integration-tests (Rails 6.1 with Ruby 3.1)
• integration-tests (Rails 7 with Ruby 2.7)
• integration-tests (Rails 7 with Ruby 3.0)
• integration-tests (Rails 7 with Ruby 3.1)
• linter-check
• smoke-test