Add Day2 module with parse_game_number function

lib/day2/day2.ex

@@ -0,0 +1,11 @@
+defmodule Day2 do
+  @moduledoc """
+  Documentation for `AdventOfCode2023`.
+  """
+
+  def parse_game_number(game_string) do
+    String.split(game_string, " ", trim: true)
+    |> Enum.take(2)
+    |> List.last() |> String.replace(":", "")
+  end
+end

test/day2/day2_test.exs

@@ -11,7 +11,7 @@ defmodule Day2Test do
       "Game 1: 7 red, 14 blue; 2 blue, 3 red, 3 green; 4 green, 12 blue, 15 red; 3 green, 12 blue, 3 red; 11 red, 2 green"
 
     large_game_string = "Game 999: 8 red"
-    assert AdventOfCode2023.get_game_string(game_string) == 1
-    assert AdventOfCode2023.get_game_string(large_game_string) == 999
+    assert Day2.parse_game_number(game_string) == "1"
+    assert Day2.parse_game_number(large_game_string) == "999"
   end
 end