Actually steel¹ is quite capable, R5RS compliant, aiming for R7Rs and it's embedable like Lua. Probably easier to use in a rust project.

https://github.com/mattwparas/steel

I know about steel as that is the Lisp I was referencing but it is unused anywhere else unlike Lua, and therefore only really maintained by one person which is not how I'd want a critical language to be used in an editor. Looks like Mitos is looking into using Wasm, from their Reddit comments.