Create a **function** named `expected_variable` that receives a string to compare and an expected string. It should return an `Option`. Every comparison should be case insensitive.
If the compared string is **not** in camel case or snake case, `expected_variable` returns `None`. You can use the `case` crate to figure that out. Otherwise, the compared string should be compared to the expected string using the `edit_distance`**function** that you have already created.
If the result of `edit_distance` has more than 50% alikeness to the expected string, considering the length of the expected string and the result of `edit_distance`, the function should return that value with a `'%'` symbol after the number.