Added program to test loading other programs from disk

hello.asm

@@ -0,0 +1,29 @@
+mov ax, 3000h
+mov ds, ax
+
+push hello_world_str
+call print
+
+;jmp $
+
+retf
+
+; print(str)
+print:
+  push bp
+  mov bp, sp
+  mov si, [bp + 4]
+  mov ah, 0eh
+  mov cx, 1
+  mov bh, 0
+print_loop:
+  lodsb
+  cmp al, 0
+  je print_exit
+  int 10h
+  jmp print_loop
+print_exit:
+  pop bp
+  ret 2
+
+hello_world_str db "Hello, World!", 13, 10, 13, 10, 0