i shall make stack machine

src/momo/stack.md

@@ -0,0 +1,26 @@
+the following document describes the stack machine used to get the correct plural form in ngettext.
+
+# instructions
+
+```
+op | description
+---|--------------------
+00 | exit
+01 | push imm
+02 | push N
+03 | add
+04 | sub
+05 | mul
+06 | div
+07 | mod
+08 | cmp eq
+09 | cmp ne
+0a | cmp gt
+0b | cmp lt
+0c | cmp ge
+0d | cmp le
+0e | cmp and
+0f | cmp or
+10 | true imm
+11 | false imm
+```