Chapter 8 examples with minor adjustments

chapter_08/examples/2_any/with_header_files/CMakeLists.txt

chapter_08/examples/2_any/with_header_files/Circle.cc

chapter_08/examples/2_any/with_header_files/Circle.hh

chapter_08/examples/2_any/with_header_files/Point.cc

chapter_08/examples/2_any/with_header_files/Point.hh

chapter_08/examples/2_any/with_header_files/Polygon.hh

chapter_08/examples/2_any/with_header_files/Triangle.cc

chapter_08/examples/2_any/with_header_files/Triangle.hh

chapter_08/examples/2_any/with_header_files/main.cc

chapter_08/examples/2_any/with_modules/CMakeLists.txt

chapter_08/examples/2_any/with_modules/Circle.ixx

chapter_08/examples/2_any/with_modules/Point.ixx

chapter_08/examples/2_any/with_modules/Polygon.ixx

chapter_08/examples/2_any/with_modules/Triangle.ixx

chapter_08/examples/2_any/with_modules/clean.sh

chapter_08/examples/2_any/with_modules/main.cc

chapter_08/examples/advent.cc

chapter_08/examples/darray_module/CMakeLists.txt

chapter_08/examples/darray_module/README.md

chapter_08/examples/darray_module/main.cc