feat: use `nix3-profile` if it has to with `-i`

[dtomvan]

Because nix-env and nix3-profile cannot be used together, I added a check for ~/.local/state/nix/profiles/profile and if it exists, it will install the target package through nix profile install instead of nix-env -iA.

Things done

• [x] nix flake check
• [x] nix build
• [x] cargo clippy
• [x] Checked ./result/bin/comma -i josm works as intended on my system with a ~/.local/state/nix/profiles/profile.
• [x] Checked that before this patch ./result/bin/comma -i josm fails.