Add day 8 implementation with input parsing and distance calculations

- Created CMakeLists.txt for day 8 and added it to the main CMakeLists.txt.
- Implemented main.cpp for day 8, including functions for parsing input, calculating distances, and processing point combinations.
- Added test and puzzle input files for day 8.

day8/test_input

@@ -0,0 +1,20 @@
+162,817,812
+57,618,57
+906,360,560
+592,479,940
+352,342,300
+466,668,158
+542,29,236
+431,825,988
+739,650,466
+52,470,668
+216,146,977
+819,987,18
+117,168,530
+805,96,715
+346,949,466
+970,615,88
+941,993,340
+862,61,35
+984,92,344
+425,690,689