Add yaml linting check in CI

[meili-bot]

This PR is auto-generated.

To avoid mistakes in the yaml files, for example, duplicated keys or wrong indentation, we decided to add a lint check on yaml files.

Additional to the .yamllint files added in this pr, the following must be added as well:

• Linting check in CI:
  Example in `tests.yml create a new job:

  yaml-lint:
    name: Yaml linting check
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Yaml lint check
        uses: ibiqlik/action-yamllint@v3
        with:
          config_file: .yamllint.yml

• Inside .yamllint, you might want to ignore some folders. For example node_modules in JS repos
  Example in .yamllint:

  ignore: |
    node_modules

Since yamllint is a python package, we cannot add a local check unless you download .yamllint.
In which case, you can check if the yaml files are correctly linted by running the following command: yamllint .

Additionally, you can use the VSCode extension YAML by redhat which automatically highlights errors.

To help users be aware of this, we recommend adding this to your contributing guide:

To check if your `yaml` files are correctly formatted, you need to [install yamllint](https://yamllint.readthedocs.io/en/stable/quickstart.html#installing-yamllint) and then run `yamllint .`

TODO

• Add the directories or files to ignore in .yamllint
• Add information in the contributing guide on this new check.

[brunoocasali]

bors merge

[meili-bors]

Build succeeded:

• integration-tests (Rails 5.2 with Ruby 2.6)
• integration-tests (Rails 5.2 with Ruby 2.7)
• integration-tests (Rails 6.1 with Ruby 2.6)
• 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