Allow write to send buffer to external program

[jrpear]

In CL Neovim you can use :w !command to send the contents of the current buffer to the stdin of any external program command. I'd like to be able to do this in VSCode Neovim.

I'm not sure exactly how this is done, but it could be as easy as checking whether a :w command has arguments before modifying it to :Write

[asvetliakov]

The right path would be add handling here:

https://github.com/asvetliakov/vscode-neovim/blob/532d4b8809f68fd90b9f4c18484a66ec158441d3/vim/vscode-file-commands.vim#L34