fix: use relative paths in generated tsconfig

[danielroe]

🔗 Linked issue

resolves #1560

❓ Type of change

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ 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

This PR uses relative paths within tsconfig paths properties, normalising whatever is provided in paths/include/exclude.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[codecov]

Codecov Report

Merging #1572 (c140293) into main (0cebdc5) will decrease coverage by 0.08%.
The diff coverage is 60.52%.

@@            Coverage Diff             @@
##             main    #1572      +/-   ##
==========================================
- Coverage   76.08%   76.00%   -0.08%     
==========================================
  Files          74       74              
  Lines        7672     7710      +38     
  Branches      753      760       +7     
==========================================
+ Hits         5837     5860      +23     
- Misses       1834     1848      +14     
- Partials        1        2       +1     

Files Changed	Coverage Δ
src/build.ts	84.18% <60.52%> (-1.76%)	⬇️