Repository: create-react-app
Issue: postcss plugins not found when compiling with CRA v5.0.0 and fomantic-ui
Labels: needs triage,issue: bug report

### Describe the bug

CRA v5 appears to be incompatible with fomantic-ui, since installing this package causes compile errors about postcss plugins not existing

### Did you try recovering your dependencies?
Yes

❯ npm --version
8.5.4

### Which terms did you search for in User Guide?

I searched for `postcss`

### Environment

> Environment Info:
> 
>   current version of create-react-app: 5.0.0
>   running from /home/davidg/.npm/_npx/c67e74de0542c87c/node_modules/create-react-app
> 
>   System:
>     OS: Linux 5.10 Ubuntu 18.04.6 LTS (Bionic Beaver)
>     CPU: (8) x64 Intel(R) Core(TM) i7-6700 CPU @ 3.40GHz
>   Binaries:
>     Node: 16.8.0 - ~/.nvm/versions/node/v16.8.0/bin/node
>     Yarn: Not Found
>     npm: 8.5.4 - ~/.nvm/versions/node/v16.8.0/bin/npm
>   Browsers:
>     Chrome: 99.0.4844.51
>     Firefox: Not Found
>   npmPackages:
>     react: ^17.0.2 => 17.0.2
>     react-dom: ^17.0.2 => 17.0.2
>     react-scripts: 5.0.0 => 5.0.0
>   npmGlobalPackages:
>     create-react-app: Not Found

### Steps to reproduce

<!--
  How would you describe your issue to someone who doesn’t know you or your project?
  Try to write a sequence of steps that anybody can repeat to see the issue.
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1. `npx create-react-app@latest cra-test --use-npm`

Follow [documented fomantic-ui install instructions:](https://fomantic-ui.com/introduction/getting-started.html#installing-via-npm)
2. `npm install --ignore-scripts fomantic-ui`
3. `cd node_modules/fomantic-ui`
4. `npx gulp install` (select defaults)
5. `npx gulp build`
7. `npm start` (this works normally)
8. `rm node_modules package-lock.json -Rf`
9. `npm install`
10. `npm start`

### Expected behavior

Successful compilation

### Actual behavior

> ERROR in ./src/index.css (./node_modules/css-loader/dist/cjs.js??ruleSet[1].rules[1].oneOf[5].use[1]!./node_modules/postcss-loader/dist/cjs.js??ruleSet[1].rules[1].oneOf[5].use[2]!./node_modules/source-map-loader/dist/cjs.js!./src/index.css)
> Module Error (from ./node_modules/postcss-loader/dist/cjs.js):
> Loading PostCSS "postcss-flexbugs-fixes" plugin failed: Cannot find module 'postcss-flexbugs-fixes'
> Require stack:
> 
> /home/davidg/cra-test/node_modules/postcss-loader/dist/utils.js
> /home/davidg/cra-test/node_modules/postcss-loader/dist/index.js
> /home/davidg/cra-test/node_modules/postcss-loader/dist/cjs.js
> /home/davidg/cra-test/node_modules/loader-runner/lib/loadLoader.js
> /home/davidg/cra-test/node_modules/loader-runner/lib/LoaderRunner.js
> /home/davidg/cra-test/node_modules/webpack/lib/NormalModule.js
> /home/davidg/cra-test/node_modules/webpack-manifest-plugin/dist/index.js
> /home/davidg/cra-test/node_modules/react-scripts/config/webpack.config.js
> /home/davidg/cra-test/node_modules/react-scripts/scripts/start.js

![image](https://user-images.githubusercontent.com/19296125/158604801-ffd37fcf-c352-420d-9369-280f6d6e446e.png)


### Reproducible demo

I hope the steps above are concise enough to serve as a reproducible demo also