cpu - Change END to increment IP, to make debugging printout work when the only line in the program is an END

cpu.js

@@ -64,6 +64,7 @@ const Instructions = {
   end: () => {
     CPU.currentInstruction.mnemonic = 'END';
     CPU.running = false;
+    CPU.IP = CPU.IP += 2;
   },
 
   store_lit: (lit) => {