Add new acceptance test scenario (020)

```
  Error: 020/lib/test.ak

    × map_2 failed
    help: ┍━ left ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┑
          │ Type mismatch expected 'integer' got 'data' │
          ┕━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┙

          should be equal to

          ┍━ right ━━━━━━━━━━━━━━━━┑
          │ (con data #d8799f0fff) │
          ┕━━━━━━━━━━━━━━━━━━━━━━━━┙
  ```

examples/acceptance_tests/020/aiken.toml

@@ -0,0 +1,2 @@
+name = "acceptance_test_020"
+version = "0.0.0"

examples/acceptance_tests/020/lib/test.ak

@@ -0,0 +1,10 @@
+pub fn map(opt: Option<a>, f: fn(a) -> result) -> Option<result> {
+  when opt is {
+    None -> None
+    Some(a) -> Some(f(a))
+  }
+}
+
+test map_2() {
+  map(Some(14), fn(n) { n + 1 }) == Some(15)
+}