2019-4: Knight Moves

Consider a chess board as an 8×8 matrix with square (1_1) in the upper left corner and square (8_8) in the lower right corner.

For those not familiar with the game of chess, the knight, generally depicted as a horse (♞), can move 2 spaces right or left and then 1 space up or down, or 2 spaces up or down and then 1 space right or left.

This means that a knight on square (5_4) can move to any of the indicated squares.

Given a 2-element vector representing the current square for a knight, return a vector of 2-element vectors representing (in any order) all the squares that the knight can move to.