Draw a hollow rectangle that is width characters wide and height rows tall. Return a list
of height strings. Cells on the outer border are #; every other cell is a space.
Examples
Input: width = 4, height = 3
Output: ["####", "# #", "####"]
Input: width = 5, height = 1
Output: ["#####"]
Constraints
1 <= width, height <= 40
Goals
- Tell border cells apart from interior cells using indices
- Handle thin boxes where every cell is on the border