docs(usage): add callout to escape invalid characters in Tailwind config

[qwerzl]

🔗 Linked issue

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

@danielroe

Closes #221. It could be confusing sometimes.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 39.86%. Comparing base (5e64174) to head (fac08e3).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #233   +/-   ##
=======================================
  Coverage   39.86%   39.86%           
=======================================
  Files          57       57           
  Lines        3419     3419           
  Branches      426      426           
=======================================
  Hits         1363     1363           
  Misses       2018     2018           
  Partials       38       38           

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