Add install task

[sabljak]

New meilisearch:install task creates an initializer file

Pull Request

Related issue

What does this PR do?

• adds a meilisearch:install task to create the meilisearch.rb initializer with template configuration
• adds changes to README.md file to include environment variables

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!

[sabljak]

@brunoocasali fixed!

Should we add the same to README.md or leave it as is?

[brunoocasali]

Should we add the same to README.md or leave it as is?

I think it is good to have the same in the README indeed!

[brunoocasali]

@sabljak I'll wait for the change before merging, thanks a lot!

[sabljak]

@brunoocasali Done! Ready for 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