leetcode2278: Percentage of Letter in String

### Description

Given a string s and a character letter, return the percentage of characters in s that equal letter rounded down to the nearest whole percent.

#### Example 1:

Input: s = "foobar", letter = "o"
Output: 33
Explanation:
The percentage of characters in s that equal the letter 'o' is 2 / 6 * 100% = 33% when rounded down, so we return 33.

#### Example 2:

Input: s = "jjjj", letter = "k"
Output: 0
Explanation:
The percentage of characters in s that equal the letter 'k' is 0%, so we return 0.

#### Constraints:

1 <= s.length <= 100
s consists of lowercase English letters.
letter is a lowercase English letter.