Expose importer in resolve method

[intrnl]

The resolve method should be given the filename that triggered the resolve, this is necessary especially for nested imports where the file could be located somewhere else.

postcssModules({
  resolve (id, from) {
    return path.resolve(from, id);
  },
});

[intrnl]

The resolver method should also be passed when resolving nested dependencies, currently the following case is impossible to do:

Let's say that the project root is also aliased to ~

/* styles/controls.css */
.control {
  border-radius: 4px;
  /* ... */
}

/* components/Button/Button.module.css */
.button {
  composes: control from '~/styles/controls.css';
  /* ... */
}

/* components/Menu/MenuItem.module.css */
.button {
  composes: button from '~/components/Button/Button.module.css';
  /* ... */
}

MenuItem.module.css succeeds in resolving Button.module.css, but because the resolve method isn't passed when parsing the source, it fails when trying to resolve its dependencies.

[KingSora]

@madyankin @intrnl created a PR for this: #142 which implements this behavior in a non-breaking way.