Adds the poise::group macro, which lets you group commands in a struct.

Use `MyStruct::commands()` to get a vec of the commands.

Removes a redundant use std::vec;

Moves the body of group into a separate function and removes match in favour of ?

More direct comparison, without iter, map and format!.

Used a match over iterator items.
Will now correctly handle paths with more than 2 segments.

Instead of quote!(), use proc_macro2::TokenStream::new()

Gives better name to command.
Adds necessary use's.

Removes hardcoded guild id and registers commands globally.

I had copied some test code and left that in.