Create a **function**`expected_variable` that receives two strings: one to be evaluated and the other to be compared to (expected) and returns an Option. Every comparison should be case insensitive.
If the evaluated string is not in camel case or in snake case (use the `case` crate for this evaluation) `expected_variable` returns `None`.
Otherwise the evaluated string should be compared to the expected string using the `edit_distance`**function** that you did in one of the previous quests.
If the result of `edit_distance` has more than 50% of 'alikeness' to the expected string, considering the length of the expected string and the result of `edit_distance`, the function should return that same percentage with a '%' symbol in front of the number.