fix: use relative source map paths and add test

[pi0]

🔗 Linked issue

❓ 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

Currently, we were always generating sourcemaps with absolute paths.

This PR makes nitro to follow default rollup behavior (generating relating sourcemap paths). This makes them portable (running in production assuming .output is adjustant to the same expected source structure and also in development mode.

It is worth to note that, we need NODE_OPTIONS=--enable-source-maps flag to lerage sourcemaps (documentation to be improved).

I have added a small test to make sure sourcemap works.

📝 Checklist

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

[codecov]

Codecov Report

Merging #1582 (5817160) into main (b8b834f) will decrease coverage by 0.10%.
Report is 2 commits behind head on main.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1582      +/-   ##
==========================================
- Coverage   76.23%   76.14%   -0.10%     
==========================================
  Files          76       76              
  Lines        7789     7788       -1     
  Branches      776      774       -2     
==========================================
- Hits         5938     5930       -8     
- Misses       1849     1855       +6     
- Partials        2        3       +1     

Files Changed	Coverage Δ
src/rollup/config.ts	90.68% <100.00%> (-0.87%)	⬇️

... and 2 files with indirect coverage changes