pad md5 string with zeroes

2016/day-17 breaks without this, for example

Author: MikeEnRegalia

src/Utils.kt

@@ -10,4 +10,4 @@ fun readInput(name: String) = File("src", "$name.txt").readLines()
 /**
  * Converts string to md5 hash.
  */
-fun String.md5(): String = BigInteger(1, MessageDigest.getInstance("MD5").digest(toByteArray())).toString(16)
+fun String.md5(): String = BigInteger(1, MessageDigest.getInstance("MD5").digest(toByteArray())).toString(16).padStart(32, '0')