Add Day 2 to CI

Author: zarethrex

.github/workflows/build_test.yaml

@@ -34,3 +34,5 @@ jobs:
                 fi
             - name: Run Day 1 Solution
               run: ./build/solutions/day_1 solutions/data/day_1.txt
+            - name: Run Day 2 Solution
+              run: ./build/solutions/day_2 solutions/data/day_2.txt