Updated exercise stories README (#346)

Author: PaulT89

building/tracks/stories/README.md

@@ -171,7 +171,8 @@ The last column includes links to the respective implementations in the tracks.
 | **making-the-grade**                   | loops                                                                  | [python](https://github.com/exercism/python/tree/main/exercises/concept/making-the-grade)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
 | **little-sisters-essay**               | string-methods                                                         | [python](https://github.com/exercism/python/tree/main/exercises/concept/little-sisters-essay)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
 | **currency-exchange**                  | numbers                                                                | [python](https://github.com/exercism/python/tree/main/exercises/concept/currency-exchange)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
-| **cater-waiter**                       | sets                                                                   | [python](https://github.com/exercism/python/tree/main/exercises/concept/cater-waiter)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
+| **cater-waiter**                       | sets                                                                   | [python](https://github.com/exercism/python/tree/main/exercises/concept/cater-waiter)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
+| **ellens-alien-game**                  | classes                                                                 | [python](https://github.com/exercism/python/tree/main/exercises/concept/ellens-alien-game)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
 | **amusement-park-improvements**        | booleans                                                               | [ruby](https://github.com/exercism/ruby/tree/main/exercises/concept/amusement-park-improvements)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
 | **log-line-parser**                    | strings                                                                | [ruby](https://github.com/exercism/ruby/tree/main/exercises/concept/log-line-parser)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
 | **assembly-line**                      | numbers, integers                                                      | [ruby](https://github.com/exercism/ruby/tree/main/exercises/concept/assembly-line), [rust](https://github.com/exercism/rust/tree/main/exercises/concept/assembly-line)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |