This is a training project from JetBrains Academy (Hyperskill).
There are two symmetric-key encryption algorithms:
"shift" - Caesar cipher for english letters only. Another symbols won't encrypt.
"unicode" - Caesar cipher, which encrypts all unicode symbols.
Command line arguments:
-alg - "unicode" or "shift" (shift by default)
-mode - "enc" or "dec"
-key
-data - string for encryption/decryption
-in - the full name of a file to read data
-out - to write data
If there is no -out argument, the app will print data to the standard output.
If there are both -data and -in arguments, the app will prefer -data over -in.