Create a `pick` function that takes an object and a string or array of strings.
This function returns a new object that contains only the key/value pairs, whose key matches with the string or a string in the array, from the object passed as an argument.
Create a `omit` function that takes an object and a string or array of strings.
This function returns a new object that contains only the key/value pairs, whose key doesn't match with the string or a single string in the array, from the object passed as an argument.
Create two functions which taken an object and a string or array of strings. They should return a new object which:
- `pick`: contains only those keys which appear in the string or array of strings.
- `omit`: contains only those keys which do not match the string, or do not appear in the array of strings.
> Those functions are pure and must not modify the given object