GETBIT key offset
@read,
@bitmap,
@fast,
Returns the bit value at offset in the string value stored at key.
When offset is beyond the string length, the string is assumed to be a contiguous space with 0 bits. When key does not exist it is assumed to be an empty string, so offset is always out of range and the value is also assumed to be a contiguous space with 0 bits.
The bit value stored at offset, one of the following:
0.1.