✅ Add solution for dictionary merge

src/python/katas/py6kyu/dictionary_merge.py

@@ -0,0 +1,23 @@
+from collections import defaultdict
+from typing import Dict, List
+
+
+def merge(*dicts: Dict[str, int]) -> Dict[str, List[int]]:
+    out = defaultdict(list)
+
+    for d in dicts:
+        for k, v in d.items():
+            out[k].append(v)
+
+    return dict(out)
+
+
+def test_merge():
+    assert merge({}, {}, {}) == {}
+    assert merge({"A": 1, "B": 2, "C": 3}) == {"A": [1], "B": [2], "C": [3]}
+
+    assert merge({"A": 1}, {"B": 2}) == {"A": [1], "B": [2]}
+    assert (
+        merge({"A": 1, "B": 2, "C": 3}, {"A": 4, "D": 5})
+        == {"A": [1, 4], "B": [2], "C": [3], "D": [5]}
+    )