add task from issue #4

TODO.md

@@ -4,5 +4,6 @@
  + [ ] remove argument `api_key` of method `Site.__init__` and add `access_token` and `auth_token` arguments to it. Also, add  usage of these arguments to method `Site.get`;
  + [X] sort constants in file `src/pystackapi/sites.py` by alphabet order;
  + [X] change type of return value in method `Site.get` and, also in `Site.get_*` from `dict` to subclass of `typing.TypedDict`;
+ + [ ] add more examples to directory `examples/`;
 
 *when you're done any of these tasks, replace `[ ]` in start of line with this task to `[X]`.*