Given a string `s` consisting of only the characters `'a'` and `'b'`, return `true` if every `'a'` appears before every `'b'` in the string. Otherwise, return `false`.

Example 1:

    Input: s = "aaabbb"
    Output: true
    Explanation:
    The 'a's are at indices 0, 1, and 2, while the 'b's are at indices 3, 4, and 5.
    Hence, every 'a' appears before every 'b' and we return true.

Example 2:

    Input: s = "abab"
    Output: false
    Explanation:
    There is an 'a' at index 2 and a 'b' at index 1.
    Hence, not every 'a' appears before every 'b' and we return false.

Example 3:

    Input: s = "bbb"
    Output: true
    Explanation:
    There are no 'a's, hence, every 'a' appears before every 'b' and we return true.

Constraints:

- `1 <= s.length <= 100`
- `s[i]` is either `'a'` or `'b'`.