Added very basic interactive shell.

makefile

@@ -12,7 +12,8 @@ objects = obj/start.o \
 	      obj/isrs.o \
 	      obj/irq.o \
 	      obj/timer.o \
-	      obj/kb.o
+	      obj/kb.o \
+	      obj/shell.o
 
 run: kernel.iso
 	qemu-system-x86_64 -cdrom kernel.iso &
@@ -26,7 +27,7 @@ obj/%.o: src/%.asm
 	nasm $(ASPARAMS) -o $@ $<
 
 kernel.bin: linker.ld $(objects)
-	mkdir obj/bin
+	mkdir -p obj/bin
 	ld $(LDPARAMS) -T $< -o obj/bin/$@ $(objects)
 #https://www.linuxjournal.com/content/add-auto-incrementing-build-number-your-build-process
 #include buildnumber.mak