codeclimate/codeclimate-rubocop

This cop is designed to help upgrade to Ruby 3.0. It will add the
comment `# frozen_string_literal: true` to the top of files to
enable frozen string literals. Frozen string literals may be default
in Ruby 3.0. The comment will be added below a shebang and encoding
comment. The frozen string literal comment is only valid in Ruby 2.3+.

### Example: EnforcedStyle: when_needed (default)
    # The `when_needed` style will add the frozen string literal comment
    # to files only when the `TargetRubyVersion` is set to 2.3+.
    # bad
    module Foo
      # ...
    end

    # good
    # frozen_string_literal: true

    module Foo
      # ...
    end

### Example: EnforcedStyle: always
    # The `always` style will always add the frozen string literal comment
    # to a file, regardless of the Ruby version or if `freeze` or `<<` are
    # called on a string literal.
    # bad
    module Bar
      # ...
    end

    # good
    # frozen_string_literal: true

    module Bar
      # ...
    end

### Example: EnforcedStyle: never
    # The `never` will enforce that the frozen string literal comment does
    # not exist in a file.
    # bad
    # frozen_string_literal: true

    module Baz
      # ...
    end

    # good
    module Baz
      # ...
    end