[rcore] Add ComputeSHA256() function

[JohnnyCena123]

No description provided.

[manuel5975p]

Just a minor suggestion, maybe pick more "unique" names for the macros otherwise it might affect other code and emit "already defined" warnings.

[raysan5]

@JohnnyCena123 thanks for the addition, added some details to be reviewed

[raysan5]

@manuel5975p That's a good point, also macros can be undefined at the end of the function.

[JohnnyCena123]

@JohnnyCena123 im getting incorrect results when i try this. can you show a minimal main.c that tests this?

already have 2 ready yeah
sha256-buffer.c
sha256-stream.c