a simple CLI script, that when given a 64-byte encoded string, it finds a suitable 4-byte prefix so that, a SHA256 hash of the prefix combined with the original string of bytes, has two last bytes as 0xca, 0xfe. Script should expect the original content of the string to be passed in hexadecimal format and should return two lines, first being the SHA256 string found and second 4-byte prefix used (in hexadecimal format).
For example: $> simple-pow 129df964b701d0b8e72fe7224cc71643cf8e000d122e72f742747708f5e3bb6294c619604e52dcd8f5446da7e9ff7459d1d3cefbcc231dd4c02730a22af9880c
Should return: 6681edd1d36af256c615bf6dcfcda03c282c3e0871bd75564458d77c529dcafe 00003997