Expand beatmapinfo-api endpoint functionality

[omkelderman]

Custom acc boiz!!

And while we're at it, lets go all out and mimic every feature of !acc including custom combo and all that fun stuff cause why not 😄

• [x] custom acc
• [ ] fun stuff thats in !acc
• [x] multiple custom acc values

[omkelderman]

custom acc done, other fun stuff later ;)