Add header support for url in order to enable authenticated requests

[peterbrandtbornholdtlee]

Description

This Pull Request adds header capabilities for the fetching of the subtitles. This is in particular useful for handling authenticated requests.

Type of Change

• [x] ✨ New feature (non-breaking change which adds functionality)
• [ ] 🛠️ Bug fix (non-breaking change which fixes an issue)
• [ ] ❌ Breaking change (fix or feature that would cause existing functionality to change)
• [ ] 🧹 Code refactor
• [ ] ✅ Build configuration change
• [ ] 📝 Documentation
• [ ] 🗑️ Chore