added elif

tests/else_if_shorthand.expected

@@ -0,0 +1 @@
+second

tests/else_if_shorthand.sl

@@ -0,0 +1,11 @@
+import stdlib/stdlib.sl
+
+word main
+    10 1 < if
+        "first" puts
+    else 1 2 < if
+        "second" puts
+    else
+        "third" puts
+    end
+end

tests/else_if_shorthand.test

@@ -0,0 +1 @@
+python main.py tests/else_if_shorthand.sl -o /tmp/else_if_shorthand > /dev/null && /tmp/else_if_shorthand