Any good? ...I mean to say: if you were forced to maintain that extension, could you dive-in?, and/or "should" it have been written in C#?, etc.
I could be wrong but guessing VSCODE extension API requires javascript, and Typescript spits out javascript, but enables compile time checking of javascript, .
I dont think you can write extension in C#, but if you can use Typescript then you definitely can do it in just javascript.
It would be neat to have the same thing for AutoLisp a "TypeAutoLisp" I really know nothing about AutoLisp but it would allow something like
(Interface Point3D (x:Real, y:Real, z:Real))
Now this would error
(setq pnt:Point3D (5, 8, "H"))