Added deal contract framework and testing documentation

pkgs/clan-cli/tests/test_with_deal.py

@@ -0,0 +1,9 @@
+import deal
+
+from clan_cli.task_manager import get_task
+
+
+# type annotations below are optional
+@deal.cases(get_task)
+def test_get_task(case: deal.TestCase) -> None:
+    case()