Matches a valid SHA-256 hash.
Contributed by @itsbrunodev
^[a-fA-F0-9]{64}$# Valid SHA-256 Hashes
abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789
ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789
# Invalid SHA-256 Hashes
abcdef0123456789abcdef
abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef