perf: ⚡️ speed up decrypt_key

Author: ZhaoQi99

pyencrypt/decrypt.py

@@ -1,9 +1,12 @@
-from pathlib import Path
 import os
+from functools import lru_cache
+from pathlib import Path
+
 from pyencrypt.aes import aes_decrypt
 from pyencrypt.ntt import intt
 
 
+@lru_cache(maxsize=None)
 def decrypt_key(cipher_key: str, d: int, n: int) -> str:
     plain_ls = list()
     for num in map(int, cipher_key.split("O")):