Repository: create-react-app
Issue: @import-normalize does not work 
Labels: needs triage,issue: bug report

### Describe the bug
According to the documentation adding **@import-normalize** in index.css should reset the browser styles but apparently it does not work and gives error as: 

**Unknown at rule @import-normalizecss(unknownAtRules)**
Here is the image with **@import-normalize**

<img width="1404" alt="Screen Shot 2020-09-27 at 9 21 24 PM" src="https://user-images.githubusercontent.com/1160546/94373709-712b6400-0107-11eb-8266-6d1a832dd3d1.png">

### Did you try recovering your dependencies?

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npm version - 6.14.4

### Which terms did you search for in User Guide?

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normalize css and reset css 

### Environment

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  System:
    OS: macOS 10.15.6
  Binaries:
    Node: 12.18.0 - /usr/local/opt/node@12/bin/node
    Yarn: 1.22.4 - /usr/local/bin/yarn
    npm: 6.14.8 - ~/dev/cph-trips/node_modules/.bin/npm
  Browsers:
    Chrome: 85.0.4183.121
    Firefox: 76.0.1
    Safari: 14.0
  npmPackages:
    react: ^16.13.1 => 16.13.1
    react-dom: ^16.13.1 => 16.13.1
    react-scripts: 3.4.3 => 3.4.3
### Steps to reproduce

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1. Download create react app using npx create-react-app
2. Add @import-normalize in index.css

### Expected behavior

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Adding  @import-normalize should reset the browser style and not show the unknown error