Add READ_UNPROTECT special dfuse command

Some devices come with write protection, and need to run this command in order to erase.

We can see the implementation in `dfu-util` here: https://gitlab.com/dfu-util/dfu-util/-/blob/master/src/dfuse.c#L219

I am happy to put in a PR, but if this library is no longer maintained, I may fork.