add `/musicbox give` command

[MrXiaoM]

I thought add a give command is necessary.

e.g.

I want to make a disc shop via other plugin. But MusicBox has just only one get command and the other plugin does not support execute as Operator (also execute command as an operator is a dangerous action). I can't do this without give command.

With give command, I just need to execute the command as console. Most of shop or menu plugin can do this with placeholder.

[Spliterash]

I don't know why I didn't do it right away, really. At first I wanted to just accept your pull, but in the process I added it to all commands