add bookshelf count option to /cenchant

[Impydude2000]

trafficstars

the option to customize the number of bookshelves and slot number in enchanting manipulation would be very nice

[Earthcomputer]

also, I'm not too sure if this is intensional or not but I can't find efficiency 5 in /cenchant

Did you not read my comment on your previous issue?

[Mhowser]

Reminds me of when I was new to github lol