Add String and Character extensions to Tools

Sources/AOC2018/tools.swift

@@ -27,4 +27,19 @@ struct Tools {
         }
         return retVal
     }
-}
+}
+
+extension Character {
+    var isAscii: Bool {
+        return unicodeScalars.first?.isASCII == true
+    }
+    var ascii: UInt32? {
+        return isAscii ? unicodeScalars.first?.value : nil
+    }
+}
+
+extension StringProtocol {
+    var ascii: [UInt32] {
+        return compactMap { $0.ascii }
+    }
+}