added factorial asm example

+set  R0 5
+push R0
+set  R1 @fact
+call R1
+pop  R0
+halt
+############
+fact:
+  set  R0 1
+  cp   SP R9
+  dec  R9
+  dec  R9
+  load R9 R1
+  set  R2 @loop
+  set  R3 @endloop
+  loop:
+    jz   R1 R3
+    mul  R0 R1
+    dec  R1
+    jmp  R2
+  endloop:
+    save R0 R9
+    ret

+set  R0 5
+push R0
+set  R8 @fact
+call R8
+pop  R0
+halt
+#############
+fact:
+  cp   SP R9
+  dec  R9
+  dec  R9
+  load R9 R0
+  set  R8 @base
+  jz   R0 R8
+  recurse:
+    dec  R0
+    push R0
+    set  R8 @fact
+    call R8
+    pop  R1
+    cp   SP R9
+    dec  R9
+    dec  R9
+    load R9 R0
+    mul  R0 R1
+    set  R8 @return
+    jmp  R8
+  base:
+    set  R0 1
+  return:
+    save R0 R9
+    ret