<p>Given two numbers <code>arr1</code> and <code>arr2</code> in base <strong>-2</strong>, return the result of adding them together.</p>
<p>Each number is given in <em>array format</em>: as an array of 0s and 1s, from most significant bit to least significant bit. For example, <code>arr = [1,1,0,1]</code> represents the number <code>(-2)^3 + (-2)^2 + (-2)^0 = -3</code>. A number <code>arr</code> in <em>array, format</em> is also guaranteed to have no leading zeros: either <code>arr == [0]</code> or <code>arr[0] == 1</code>.</p>
<p>Return the result of adding <code>arr1</code> and <code>arr2</code> in the same format: as an array of 0s and 1s with no leading zeros.</p>