Change publisher to Nix org and verify

[uncenter]

It's a shame that this extension isn't the most popular/downloaded extension in VSCode.

I think changing the publisher from @jnoortheen's personal account to a Nix organization account and verifying the Nix organization account as an official publisher (gives the extension a blue checkmark) will help with boosting the popularity of this extension. I'd also like to second #306 here, I think that will clarify this extension's "official-ness" even further.