Use common error codes

[jonbarrow]

Changes:

Makes Bandwidth pull from https://github.com/PretendoNetwork/error-codes rather than his own error codes, like we discussed on Discord. Whenever the centralized repository updates, Bandwidth can also update to get the new error codes.

Also changed the embed format slightly to link to the new support pages.

• [x] I have read and agreed to the Code of Conduct.
• [x] I have read and complied with the contributing guidelines.
• [ ] What I'm implementing was an approved issue.
• [x] I have tested all of my changes.