Class methods get analyzed as instance methods

Currently class methods using the `class << self` definition are being analyzed as instance methods. Example:

```ruby
module Nokogiri
  module CSS
    class << self
      def parse(selector)
        Parser.new.parse(selector)
      end
    end
  end
end
```

https://gem.sh/gems/nokogiri/v1.15.3/module/Nokogiri::CSS
