Update discord.js dependency
The currently used version (12.5.3) isn't maintained anymore and has some security issues nowadays. However, a lot of breaking changes have been introduced in version 13, requiring us to modify a lot of code.
The currently used version (12.5.3) isn't maintained anymore and has some security issues nowadays. However, a lot of breaking changes have been introduced in version 13, requiring us to modify a lot of code.