Add an extension to create a MD5 hash from a string

[JulianYu]

[ ] I've read, understood, and done my best to follow the Contributing guidelines before opening this issue.

What did you expect to happen?

how about add something like md5

[omaralbeik]

@JulianYu, thats a nice extension to have, could you please submit a pull request and I'll make sure to review it and get it merged in as soon as I can 👍

[omaralbeik]

I found this stackoverflow thread that has a suggested way of doing this.

[SD10]

@omaralbeik What do you think about this? SwifterSwift has very little to no limitations when it comes to which extensions we accept into the project, but I think avoiding adding cryptography extensions is a healthy limitation.

[omaralbeik]

@SD10 I agree. let's not get into cryptography for now

[omaralbeik]

@JulianYu Thank you for bringing this to the table. We don't think SwifterSwift is a good fit for cryptography extensions at the moment, CryptoSwift is taking care of this :)