Add support for getArrayUnsignedBytes()

[ttk]

A simple addition to this library to allow for reading multiple unsigned bytes into an array. Unit tests added and passing.

Without this function it was required to do this:

$bytes = $this->buffer->getArrayBytes(5);
$unsigned_bytes = array_map(fn($v) => $v & 0xff, $bytes);

with this patch, you can now simply do this:

$unsigned_bytes = $this->buffer->getArrayUnsignedBytes(5);