add encrypt-data-using-hc-256

[williballenthin]

mandiant/capa-testfiles#300

inspired by here: https://blu3eye.gitbook.io/malware-insight/moonstone-sleet-trojaned-putty

[williballenthin]

we already have HC-128, which is a similar but different algorithm. in particular:

HC-128 is similar in function, and reduces each of key length, nonce, number of words in the tables P and Q, and number of table updating steps by half.[2]
https://en.wikipedia.org/wiki/HC-256

that rule does not match the new example.

[mike-hunhoff]

great, thank you @williballenthin !