Write a function that reverses a string. The input string is given as an array of characters `s`.

You must do this by modifying the input array in-place with `O(1)` extra memory.

Example 1:

    Input: s = ["h","e","l","l","o"]
    Output: ["o","l","l","e","h"]

Example 2:

    Input: s = ["H","a","n","n","a","h"]
    Output: ["h","a","n","n","a","H"]

Constraints:

- `1 <= s.length <= 105`
- `s[i]` is a printable ascii character.