Write a function in JavaScript that finds the biggest element inside a matrix.

The input comes as array of arrays, containing number elements (2D matrix of numbers).

**Examples:**

**Input:**

[[20, 50, 10],

[8, 33, 145]]

**Output:**

145

**Input:**

[[3, 5, 7, 12],

[-1, 4, 33, 2],

[8, 3, 0, 4]]

**Output:**

33

The output is the return value of your function.

Find the biggest element and return it.