Added time complexity for berlekamp massey (#131)

Author: Chillee

content/numerical/BerlekampMassey.h

@@ -9,6 +9,7 @@
  * Should work on any field, but numerical stability for floats is not guaranteed.
  * Output will have size $\le n$.
  * Usage: BerlekampMassey({0, 1, 1, 3, 5, 11}) // {1, 2}
+ * Time: O(N^2)
  * Status: bruteforce-tested mod 5 for n <= 5 and all s
  */
 #pragma once