feat(content): function signatures + test cases

backend/data/questions/calculate-money-in-leetcode-bank.yaml

@@ -8,6 +8,30 @@ categories:
 patterns:
   - prefix-sum
 
+function_signature: "def total_money(n: int) -> int:"
+
+test_cases:
+  visible:
+    - input: { n: 4 }
+      expected: 10
+    - input: { n: 10 }
+      expected: 37
+    - input: { n: 20 }
+      expected: 96
+  hidden:
+    - input: { n: 1 }
+      expected: 1
+    - input: { n: 7 }
+      expected: 28
+    - input: { n: 8 }
+      expected: 30
+    - input: { n: 14 }
+      expected: 63
+    - input: { n: 100 }
+      expected: 678
+    - input: { n: 1000 }
+      expected: 7089
+
 description: |
   Hercy wants to save money for his first car. He puts money in the Leetcode bank **every day**.