Begin implementing staged undo system

bulk_reminders/undo.py

@@ -0,0 +1,20 @@
+import json
+import os
+
+stages = []
+
+
+def load() -> None:
+    """Load data from the undo history file"""
+    with open('history.json', 'r') as history:
+        stages = json.load(history)
+
+
+def save() -> None:
+    """Save data to the undo history file."""
+    with open('history.json', 'w') as history:
+        stages = json.dump(history)
+
+
+if os.path.exists('history.json'):
+    load()