It has plugin architecture that allows anyone to build plugins for Yack. Once out of beta, users will be able to install custom plugins directly from GitHub. Plugins must be written in TypeScript though.
Will you also release Linux and Windows versions or is it meant to be Mac-only?
I don't mean TypeScript is much worse. Python just is the first thing to come to my mind as "right tool for the job" when it's about textual content processing. I'm not saying "please implement Python support instead", I'm just explaining why I've mentioned Python first. TypeScript is great too.