message: add test to cover numeric prefixed s operator
diff: @@ -213,4 +213,11 @@ suite("Mode Insert", () => {
  end: ['test==|=']
  });
  + newTest({
  + title: "Can perform change char (s) command prefixed with count",
  + start: ['tes|ttest'],
  + keysPressed: '3s=====<Esc>',
  + end: ['tes====|=st']
  + });
  +
  });
  