Added Factorial in Racket

[zafar-hussain]

Congrats on taking the first step to contributing to the Sample Programs repository maintained by The Renegade Coder! For simplicity, please make sure that your pull request includes one and only one contribution.

Complete the Applicable Sections Below

Find which section best describes your pull request and make sure you fill it out. To start, let us know which issue you've fixed.

• I fixed #your-issue-number-here

Code Snippets

• I named the pull request using Added/Updated <Sample Program> in <Language> format
• I created/updated the language README
• I added the sample program name to the README
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Documentation

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• I followed the applicable article template
  • I added/updated a language article (i.e. The Python Programming Language)
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Testing

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Notes

Feel free to describe what you added or updated.

[auroq]

See my comments in #1843:

#1843 (comment)

[jrg94]

Looks good! 🚦