[Feature Request] Add more ops like and/or/overlay/copy/etc.

[yeahdongcn]

I want to use bitstring in a project and finally find this repo. This single-bit ops fit my requirements very well. But I noticed that certain ops between 2 bitstrings are still in your TODO list. So I'm wondering whether it is possible to get these features recently. It would be very helpful to me. Thanks.

[arl]

Hi. I don't have much time to work on bitstring at the moment.

What would the most important missing API for you at the moment?

PR are welcome by the way ;-)