Supporting a more secure hash for email addresses

[simondean]

Hi. staticman supports only md5 hashing, e.g. to hash an email address field. md5 is an insecure hashing algorithm. It's probably possible to convert md5 hashes to real email addresses using something like a rainbow table attack. Would it be possible to add support for a more secure hashing algorithm like SHA-256? Thanks

https://github.com/eduardoboucas/staticman/blob/5d7ed7708775e3d4864382cca88d2d73ff875864/lib/Transforms.js