Add iostream and initialization

ch_0/hello_world/Makefile

@@ -0,0 +1,8 @@
+all:
+	g++ main.cpp -o main -O2 -DNDEBUG -pedantic-errors -Wall -Weffc++ -Wextra -Wconversion -Wsign-conversion -std=c++23
+
+debug:
+	g++ main.cpp -o main -ggdb -pedantic-errors -Wall -Weffc++ -Wextra -Wconversion -Wsign-conversion -std=c++23
+
+clean:
+	rm -r main