Repository: create-react-app
Issue: React-scripts v4 ignores the .eslintignore file at the root when using a monorepo
Labels: needs triage,issue: bug report

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### Describe the bug

I have a monorepo that is managed by Lerna and yarn workspaces.
All eslint and prettier configs are hosted in the root of the monorepo, CRA v4 ignores the .eslintignore and .prettierignre 
and lints files and folders that are skipped in .eslintignore and .prettierignre.
running eslint via the command line or vs code load the  .eslintignore and .prettierignre and respects the ignored files,
back in CRA v3 this was working.

### Environment

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Environment Info:

  current version of create-react-app: 4.0.0
  running from C:\Users\user\AppData\Local\Yarn\Data\global\node_modules\create-react-app

  System:
    OS: Windows 10 10.0.19041
    CPU: (8) x64 Intel(R) Core(TM) i7-8650U CPU @ 1.90GHz
  Binaries:
    Node: 14.13.1 - C:\Program Files\nodejs\node.EXE
    Yarn: 1.22.5 - C:\Program Files (x86)\Yarn\bin\yarn.CMD
    npm: 6.14.8 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Chrome: 86.0.4240.111
    Edge: Spartan (44.19041.423.0), Chromium (86.0.622.58)
    Internet Explorer: 11.0.19041.1
  npmPackages:
    react: Not Found
    react-dom: ^17.0.1 => 17.0.1
    react-scripts: Not Found
  npmGlobalPackages:
    create-react-app: Not Found

### Steps to reproduce

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1.  Bootstrap a monorepo using lerna.
2. Add eslint and prettier config files alongside with .eslintignore file at the root
3. Bootstrap a CRA app inside the packages folder and remove eslintConfig from package.json
4. Add a js or ts file and ignore it in the .eslintignore file
5. Run yarn dev or build

### Expected behavior

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If the ignored file contains eslint or prettier error CRA shouldn't report it in the terminal

### Actual behavior

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CRA lists the files that supposed to be ignored when running dev or build scripts and displays the errors in the terminal

### Reproducible demo

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https://github.com/ahrbil/cra-v4-monorepo-eslint
1. Install the dependencies using yarn
2. Run yarn start
3. You should see this log :
``` 
@cra-v4-monorepo-eslint/web: Starting the development server...
@cra-v4-monorepo-eslint/web: Failed to compile.
@cra-v4-monorepo-eslint/web: src\ignore-this-file.tsx
@cra-v4-monorepo-eslint/web:   Line 7:42:  'children' is missing in props validation  react/prop-types
@cra-v4-monorepo-eslint/web:   Line 7:52:  'color' is missing in props validation     react/prop-types
@cra-v4-monorepo-eslint/web:   Line 8:10:  Delete `·`                                 prettier/prettier
@cra-v4-monorepo-eslint/web: Search for the keywords to learn more about each error. 
```
even if the `ignore-this-file.tsx` file is ignored in the .eslintignore file, it is still being checked and makes the build fails to compile

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