Loader options lost when previewMdx2 is activated

[quantizor]

Describe the bug

I'm not 100% sure what's going on, but it appears the remark plugins that are set up in https://github.com/storybookjs/storybook/blob/4b47793e118f091971f2a453d486c5f01875811d/addons/docs/src/preset.ts#L55-L58 are not making it through to this new MDX2 loader.

When inspecting the options pulled from webpack in

mdx2-csf/loader.js

Line 17 in d607151

const queryOptions = this.getOptions ? this.getOptions() : getOptions(this);

they're totally blank (skipCsf is missing, as well as the plugins...)

The effect of this is that header links in mdx no longer are applied.