add readme & docstrings

model.py

@@ -6,9 +6,14 @@ from uuid import UUID
 
 @dataclass
 class Transaction:
+    """Represents an Actual Budget transaction to be submitted.
+
+    See: https://actualbudget.org/docs/api/reference#transaction for field descriptions
+    """
+
     account: UUID
     date: date
-    amount: Decimal
+    amount: Decimal  # Note: decimal dollars, JS shim will convert to cents as described in the API
     payee: str  # imported_payee in API
     notes: str
     imported_id: str