feat(meta): update mainProgram to "cratedocs"

- Replaced `mainProgram` reference from `cargoFile.name` to `"cratedocs"`.

default.nix

@@ -34,6 +34,6 @@ in rustPlatform.buildRustPackage {
 
   meta = {
     license = lib.licenses.mit;
-    mainProgram = cargoFile.name;
+    mainProgram = "cratedocs";
   };
 }