Rotate String

You are given two strings s and goal.
Return true if and only if s can become goal after performing some number of left rotations.

A left rotation (shift) means removing the first character of s and appending it to the end.

Example:
"abcde" → "bcdea" → "cdeab" → …

To determine if goal is a rotation of s, notice that any rotation of s will always appear as a substring of s + s.