## Clean the list
### Instructions
Create a file `shopping.py` that contains a function `clean_list` which takes in a list of strings and performs the following operations on each list item:
- Removes all spaces before and after (but not between words).
- Capitalizes the first letter (first letter only, other ones should be to lowercase).
- Adds its index number before a separator `x/ ` .
- An empty list as input should return an empty list as output.
- And don't forget the milk! (add it at the end of the list if missing).
### Usage
Here is an example of how to use the `clean_list` function:
```python
import shopping
shopping_list = ['tomatoes', 'pastas', 'milk', 'salt']
print(shopping.clean_list(shopping_list))
```
This will output:
```console
['1/ Tomatoes', '2/ Pastas', '3/ Milk', '4/ Salt']
```
### References
[string strip method ](https://www.w3schools.com/python/ref_string_strip.asp )
[string capitalize method ](https://www.w3schools.com/python/ref_string_capitalize.asp )
