Add items iterator for slices

lib/system.nim

@@ -1738,6 +1738,12 @@ iterator items*(E: typedesc[enum]): E =
   for v in low(E)..high(E):
     yield v
 
+iterator items*[T](s: Slice[T]): T =
+  ## iterates over the slice `s`, yielding each value between `s.a` and `s.b`
+  ## (inclusively).
+  for x in s.a..s.b:
+    yield x
+
 iterator pairs*[T](a: openArray[T]): tuple[key: int, val: T] {.inline.} =
   ## iterates over each item of `a`. Yields ``(index, a[index])`` pairs.
   var i = 0