Add support Y in visual mode

[shotaAkasaka]

Fixes #573

[jpoon]

Noice! 🎉 .

edit: I should use reactions more

[johnfn]

If you directly extend the YankOperator, then this will act as an operator as well, meaning it will be able to be combined with motions to do actions (d is an operator because you can do dw, and c is an operator because you can do c$, etc.)

That's not what you want here. You want to create and execute a new YankOperator, running it across the entire current line.

Make sense? :)

[shotaAkasaka]

@johnfn Thanks for yout comment.
I have to create anad execute new YankOperator,like that?

@RegisterAction
export class ShiftYankVisualModeOperator extends BaseOperator {
    public keys = ["Y"];
    public modes = [ModeName.Visual];

    public async run(vimState: VimState, start: Position, end: Position): Promise<VimState> {
      // execute 
    }
}

[johnfn]

I mean something more along the lines of

new YankOperator().run(vimState, position.getLineStart(), position.getLineEnd())

(That is untested code...)

[johnfn]

There we go. :)

Thanks for the PR, @shotaAkasaka!