Add Justification functions

[safareli]

https://www.stackage.org/haddock/lts-8.21/text-1.2.2.1/Data-Text.html#g:9

justifyRight :: Int -> Char -> String -> String
justifyLeft :: Int -> Char -> String -> String
center :: Int -> Char -> String -> String

Let me know if it's desired addition 🎈

[hdgarrood]

I'd be in favour. At the same time we should also add codepoint-based versions e.g. justifyRight :: Int -> CodePoint -> String -> String to Data.String.CodePoints.