Add Day 1, Puzzle 2 solution

src/Main.hs

@@ -1,6 +1,6 @@
 module Main (main) where
 
-import Day01 (day01_1)
+import Day01 (day01_1, day01_2)
 import System.Environment (getArgs)
 
 main :: IO ()
@@ -8,8 +8,11 @@ main = do
   args <- getArgs
   case args of
     "1" : "1" : _ -> day01_1
+    "1" : "2" : _ -> day01_2
     "1" : _ -> do
       day01_1
+      day01_2
     "all" : _ -> do
       day01_1
+      day01_2
     _ -> error "Not implemented"