Added functionality to get membership list

[mariosanz92]

This functionality allows to get all the membership list from an specific user ID

-Documentation of endpoint added from twitter API:

https://developer.twitter.com/en/docs/twitter-api/lists/list-members/api-reference/get-users-id-list_memberships

• Endpoint: https://api.twitter.com/2/users/:id/list_memberships

[igorbrigadir]

Thanks for your contribution! I'm actually in the middle of implementing this for the command line too, so i'm going to go ahead and merge this here, and then add the changes to the command2.py and the other list commands according to #572 in a separate PR. This PR takes care of a chunk of it already, thanks!

[igorbrigadir]

I added in some changes in expansions.py in 093eb5c to align it with how the other endpoints are handles too. The rest of the CLI changes are going to be in #606