feat(tvix/eval): add initial value representation

Change-Id: I427a04e89994662df2750dffe21991bad48aab15
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6066
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>

tvix/eval/src/main.rs

@@ -6,6 +6,7 @@ use std::{
 
 mod errors;
 mod eval;
+mod value;
 
 fn main() {
     let mut args = env::args();