Challenge:
Write a Python script that performs basic encryption and decryption using a Caesar cipher. The script should:
Prompt the user to choose between encryption and decryption.
If the user chooses encryption:
Prompt the user to input a plaintext message.
Prompt the user to input a shift value (an integer) for the Caesar cipher.
Encrypt the plaintext message using the Caesar cipher with the given shift value.
Print the encrypted message.
If the user chooses decryption:
Prompt the user to input an encrypted message.
Prompt the user to input the shift value used for encryption.
Decrypt the encrypted message using the Caesar cipher with the given shift value.
Print the decrypted message.
Ensure that the script handles both uppercase and lowercase letters properly (i.e., maintains the case of the letters).
