sha256(string) - return sha256 checksum from string.
Examples
local crypto = require("crypto")
-- md5
if not(crypto.md5("1\n") == "b026324c6904b2a9cb4b88d6d61c81d1") then
error("md5")
end
-- sha256
if not(crypto.sha256("1\n") == "4355a46b19d348dc2f57c046f8ef63d4538ebb936000f3c9ee954a27460dd865") then
error("sha256")
end