Sets the byte at the specified
byteOffset in this object to the
two's complement binary representation of the specified
must fit in a single byte.
In other words,
value must be between -128 and 127, inclusive.
Throws RangeError if
byteOffset is negative, or
greater than or equal to the length of this object.
void setInt8(int byteOffset, int value) => _unsupported();