AOC2023: implement day3

Solution to second puzzle is not optimal, it definately should be
O(1) space, but I didn't want to think about it.

userspace/aoc2023/day3/CMakeLists.txt

@@ -0,0 +1,22 @@
+cmake_minimum_required(VERSION 3.26)
+
+project(aoc2023_day3 CXX)
+
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2023_day3 ${SOURCES})
+target_compile_options(aoc2023_day3 PUBLIC -O2 -g)
+target_link_libraries(aoc2023_day3 PUBLIC libc ban)
+
+add_dependencies(aoc2023_day3 libc-install ban-install)
+
+add_custom_target(aoc2023_day3-install
+	COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_BINARY_DIR}/aoc2023_day3 ${BANAN_AOC2023_BIN}/day3
+	DEPENDS aoc2023_day3
+	DEPENDS aoc2023_always
+)
+
+add_dependencies(aoc2023 aoc2023_day3)
+add_dependencies(aoc2023-install aoc2023_day3-install)