Docs: Raw support for mjs, jsx, and tsx files

[42shadow42]

What I did

Enabled support for loading truly raw mjs,jsx, and tsx files by disabling the babel-loader when the raw query is set.

How to test

1. Run a sandbox for template, e.g. yarn task --task sandbox --template react-webpack/18-ts
2. Open Storybook in your browser
3. Comment the webpackFinal overrides in .storybook/main.ts
4. Access ?path=/docs/addons-docs-stories-mdx-raw-source--docs
5. Verify you see:

import React, { Fragment } from 'react';

export const MY_VALUE_I_WANT_TO_SHOW_IN_STORY = 'Hello World!';

export const RawSource = () => {
  return <Fragment>{MY_VALUE_I_WANT_TO_SHOW_IN_STORY}</Fragment>;
};

Instead of:

import React, { Fragment } from "react";
export const MY_VALUE_I_WANT_TO_SHOW_IN_STORY = "Hello World!";
export const RawSource = () => {
  return /* @__PURE__ */ React.createElement(Fragment, null, MY_VALUE_I_WANT_TO_SHOW_IN_STORY);
};

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests)
• Make sure to add/update documentation regarding your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Maintainers

• If this PR should be tested against many or all sandboxes,
  make sure to add the ci:merged or ci:daily GH label to it.
• Make sure this PR contains one of the labels below.

["cleanup", "BREAKING CHANGE", "feature request", "bug", "documentation", "maintenance", "dependencies", "other"]

[42shadow42]

I hope it's okay, I'm marking this as ready for review despite a lack of test automation because I'm not sure how to get started testing this feature automatically, as is it can't even be tested manually without making manual modifications to the testing scaffolds. After taking a glance if you could point me in a good direction I'll continue on those parts of the PR.

[yannbf]

Hey @42shadow42 thank you so much for your contribution! Let's involve @ndelangen to help you get started with testing, and @jonniebigodes to chime in regarding possible documentation changes.

thanks!

[yannbf]

Hey @ndelangen do you think this is good to (rebase then) merge?