Repository: create-react-app
Issue: Documentation for "measuring performance" is missing from create-react-app.dev
Labels: stale,needs triage,issue: bug report

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### Describe the bug

There is a link in `index.tsx` that is supposed to link to a "measuring performance" page but directed to a 404 page.
In the file, the link is `https://bit.ly/CRA-vitals` and redirects to `https://create-react-app.dev/docs/measuring-performance`

### Did you try recovering your dependencies?

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Not applicable

### Which terms did you search for in User Guide?

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Page isn't found in create-react-app...
Searched for `performance`, `measuring` and `measuring performance`.

### Environment

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```
Environment Info:

  current version of create-react-app: 4.0.0
  running from /home/fc-randy-h/.config/yarn/global/node_modules/create-react-app

  System:
    OS: Linux 4.19 Ubuntu 18.04.5 LTS (Bionic Beaver)
    CPU: (8) x64 Intel(R) Core(TM) i7-4910MQ CPU @ 2.90GHz
  Binaries:
    Node: 14.13.1 - /home/linuxbrew/.linuxbrew/bin/node
    Yarn: 1.22.10 - /home/linuxbrew/.linuxbrew/bin/yarn
    npm: 6.14.8 - /home/linuxbrew/.linuxbrew/bin/npm
  Browsers:
    Chrome: Not Found
    Firefox: Not Found
  npmPackages:
    react: ^17.0.1 => 17.0.1 (16.13.1)
    react-dom: ^17.0.1 => 17.0.1 (16.13.1)
    react-scripts: Not Found
  npmGlobalPackages:
    create-react-app: Not Found
```

### Steps to reproduce

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1. Init new app with `yarn create react-app <name> --template typescript`
2. Open `index.tsx` file
3. Open link in comment (around line 16)

### Expected behavior

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Should have redirected to a proper doc page

### Actual behavior

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404 error, unable to find page
![image](https://user-images.githubusercontent.com/52173775/97057770-d4f75000-1540-11eb-96cc-3a976f1813ed.png)

### Reproducible demo

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Line 16 of `src/index.tsx`
https://github.com/randy-halim/cra-broken-perf-link

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