feat(provider): add railway support

[o-az]

🔗 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)
• [x] ✨ 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

Adding support for https://railway.app. Not entirely sure I'm doing this right. Please let me know if that's not how it should be.

Ref: https://docs.railway.app/reference/variables#railway-provided-variables

📝 Checklist

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

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (bfaedd7) 80.46% compared to head (e7af614) 80.63%. Report is 2 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #106 +/- ## ========================================== + Coverage 80.46% 80.63% +0.16% ========================================== Files 10 10 Lines 343 346 +3 Branches 32 32 ========================================== + Hits 276 279 +3 Misses 61 61 Partials 6 6 ```

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