Add another failing example (e)

```
  Error:
    × Main thread panicked.
    ├─▶ at crates/lang/src/uplc.rs:1518:45
    ╰─▶ called `Option::unwrap()` on a `None` value
    help: set the `RUST_BACKTRACE=1` environment variable to display a backtrace.
  ```

examples/tests/e/aiken.toml

@@ -0,0 +1,2 @@
+name = "test_e"
+version = "0.0.0"

examples/tests/e/lib/main.ak

@@ -0,0 +1,16 @@
+use aiken/builtin.{head_list}
+
+pub fn head(xs: List<a>) -> Option<a> {
+  when xs is {
+    [] -> None
+    _ -> Some(head_list(xs))
+  }
+}
+
+test head_1() {
+  head([1, 2, 3]) == Some(1)
+}
+
+test head_2() {
+  head([]) == None
+}