Add new acceptance test scenario: 063

examples/acceptance_tests/063/lib/tests.ak

@@ -0,0 +1,17 @@
+fn must_be_signed(signatories) {
+  when signatories is {
+    [] -> {
+      trace "no signatories"
+      False
+    }
+    [sig, ..] -> (sig == "#ffff")?
+  }
+}
+
+fn must_say_hello(msg) {
+  msg == "Hello, World!"
+}
+
+test foo() {
+  must_be_signed(["#f000"])? && must_say_hello("Hello, World!")? || True
+}