Add support for opendoas

[CaptainJawZ]

I saw that there is a closed PR that tried to add support to other privilege elevation programs, not sure as to why it was never merged, so I apologize if this PR is inappropriate because of that, that said, if the PR is welcomed here is what I added:

only support for doas, with an environment variable NH_USE_DOAS, if set to 1 or true, it will, well... use doas instead of sudo.

To prevent any breaking changes, I kept all the sudo logic within main.rs intact, just enclosed it on a clause to only add flags (--preserve-env and -A) if sudo is the selected helper.

For command.rs and main.rs I also added checks so doas is not run when on macos, but this is temporary, as my job will later this year provide me with a macbook, I could see about adding support for macos, at the moment I can only test on nixos/liunx.

I did a bunch of tests with and without the flag (so testing sudo and doas) and it seems like nothing broke, I hope this helps. Of course if any changes are required I will be more than welcomed to implement them.

[midischwarz12]

This seems like a duplicate of #92 but restricted to only doas. However, I think #92 would be a better option to merge since it is more generic.

[CaptainJawZ]

This seems like a duplicate of #92 but restricted to only doas. However, I think #92 would be a better option to merge since it is more generic.

yeah it does, but at the time I opened this PR, #92 was abandoned for over six months I believe, I see that it got activity some weeks ago again, which is good, if so, this PR can be closed.

[NotAShelf]

Thank you for your efforts @CaptainJawZ. Seeing #92 is picked back up and has a more comprehensive approach, I'll be going forward with it. Though, let the record show that I appreciate your PR. Unfortunately Viper and I could not come to a decision on this before 92 was updated.

Closing in favor of #92.