docs(python): update README to include new `py` alias (#9995)

plugins/python/README.md

@@ -11,6 +11,7 @@ plugins=(... python)
 
 | Command          | Description                                                                     |
 |------------------|---------------------------------------------------------------------------------|
+| `py`             | Runs `python`                                                                   |
 | `ipython`        | Runs the appropriate `ipython` version according to the activated virtualenv    |
 | `pyfind`         | Finds .py files recursively in the current directory                            |
 | `pyclean [dirs]` | Deletes byte-code and cache files from a list of directories or the current one |