Revert "remove program.cairo"

This reverts commit 75b15d9.

Author: FrancoGiachetta

program.cairo

@@ -0,0 +1,11 @@
+use core::box::BoxTrait;
+
+enum MyEnum {
+    A: felt252,
+    B: u128,
+}
+
+fn run_test() -> MyEnum {
+    let x = BoxTrait::new(MyEnum::A(1234));
+    x.unbox()
+}