Isn't Swift a proprietary Apple thing? Are there any implementations other than theirs? It's not obvious to me why a language designed for proprietary UI development would have any special suitability for text editor scripting.
Were I to add a scripting language into the editor I maintain, there are half a dozen candidates which quickly come to mind; if none proved suitable, I would probably end up designing a new language, tailored to my purpose, before it would occur to me to use some heavyweight, VM-driven beast like Swift (or C# or Java).