Added flag that provides the option to launch qutebrowser without any profile

[chaorace]

When provided, this new flag adds the option to launch qutebrowser without any profile applied, as if it were launched normally.

When enabled, a special profile (called "default", but can be changed via the flag's optional parameter) is shown in --list output and within the --choose menu. Selecting this special profile via --load or --choose is how the user tells the program to open qutebrowser without any applied profile.

[jtyers]

Thanks for your work on this @chaorace . I've re-implemented qutebrowser-profile in Python which solves a few headaches with its implementation. Would it be possible to re-work your implementation in Python?

[chaorace]

Sure @jtyers I can port my change but would you mind if prior to that I submitted a PR which provides a Nix Flake for this project? It'd make my life a lot easier development-wise while also no doubt pleasing any other NixOS users out there