feat(joinURL): handle segments with ../

[danielroe]

🔗 Linked issue

resolves #37

❓ 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

Was reminded of this while implementing nuxt/fonts#24 (because we are rendering /_nuxt/../_fonts/some-font.woff2 instead of just /_fonts/some-font.woff2. It would be nice to get these URLs rendering better, which I'd like before we move it out of the experimental flag.

Would welcome any thoughts on a better algorithm. 🙏

📝 Checklist

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