v0.21.0

What's Changed

• Move config initialization code outside of course library by @martinmr in #301
• Fix clippy warnings in tests by @martinmr in #302
• Fix test coverage by @martinmr in #303
• Update to rust 1.78 by @martinmr in #304
• Add interface for getting and setting user preferences by @martinmr in #305
• Update comments in graph module by @martinmr in #306
• Modify transcription exercises to include external link by @martinmr in #307
• Add module to download transcription assets by @martinmr in #298
• Add more transcription downloader tests by @martinmr in #308
• Rename TranscriptionDownloader methods by @martinmr in #309

Full Changelog: v0.20.0...v0.21.0