Given a string s, the power of the string is the maximum length of a non-empty substring that contains only one unique character. Return the power of the string. Example 1: Input: s = "leetcode" Output: 2 Explanation: The substring "ee" is of length 2 with the character 'e' only. Example 2: Input: s = "abbcccddddeeeeedcba" Output: 5 Explanation: The substring "eeeee" is of length 5 with the character 'e' only. Example 3: Input: s = "triplepillooooow" Output: 5 Example 4: Input: s = "hooraaaaaaaaaaay" Output: 11 Example 5: Input: s = "tourist" Output: 1 Constraints: 1 <= s.length <= 500 s contains only lowercase English letters.