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/CMakeLists.txt

@@ -0,0 +1,2 @@
+ # Use top-level helper to add the target and copy input files
+ aoc_add_day(day8 "${CMAKE_CURRENT_SOURCE_DIR}" main.cpp)