Add an option to not concatenate a type with a `locals` key

[raphael-leger]

The generated d.ts files contain the following:

{
  /** WARNING: Only available when `css-loader` is used without `style-loader` or `mini-css-extract-plugin` */
  locals: AnimalScssNamespace.IAnimalScss;
};

As stated, this code is not always useful.
In this case, it takes space and complexifies the type readability.

It would be great to add an option to disable the generation of this code.