Update README.md

[M1tsumi]

• Project Name: SwiftDisc
• Project URL: https://github.com/M1tsumi/SwiftDisc
• Project Description: A Discord API Wrapper
• Why it should be added to awesome-swift: There are no other Discord API Libraries included on the list and SwiftDisc has near complete endpoint coverage and has optimal documentation!
• At least 15 stars (GitHub project)
• Support Swift 5
• Updated contents.json instead of README
• Lib is fully open sourced, written in Swift and not a wrapper over compiled lib
• Description does not say "written in Swift" or variant 🤓