Fix SyntaxError for *.mdx files in test output (#754)

[toptalo]

Fixes #754

PR Checklist

• My branch is up-to-date with the Upstream master branch.
• The unit tests pass locally with my changes (if applicable).
• I have added tests that prove my fix is effective or that my feature works (if applicable).
• I have added necessary documentation (if appropriate).

Short description of what this resolves:

I have add @babel/preset-react (https://git.io/JfeDR) to the 'presets' section of Babel config as it have been recommended in tests output

Changes proposed in this Pull Request:

• add .babelrc config file

[vercel]

This pull request is being automatically deployed with Vercel (learn more).
To see the status of your deployment, click below or on the icon next to each commit.

🔍 Inspect: https://vercel.com/dip-trasformazione-digitale/design-react-kit/AQfpGWSrSx3WxEDDc2Fx13FnBtx8
✅ Preview: https://design-react-kit-git-fork-to-55cc7d-dip-trasformazione-digitale.vercel.app

[dej611]

I can see the fix works, but I would prefer to have a jest-only configuration to avoid any confusion, rather than a generic .babelrc file.

You can point Jest to a specific js file for this type of things so that it will become clear that is not a build configuration thing. Yu can use as reference the react-router config with its jest-transformer.js file and how they pointed to that from the jest main config file.

[toptalo]

I'm not sure, maybe it would be better to move jest-transformer.js to scripts/jest-transformer.js?

[dej611]

I'm not sure, maybe it would be better to move jest-transformer.js to scripts/jest-transformer.js?

I think that's ok as it is now.

[dej611]

🎉 Thanks for your contribution!
Looks great 👍

[toptalo]

Thank you!