fix?: automatically add user to docker group when needed

[hollowshiroyuki]

Using sudo is annoying, it remembers your password for 10 minutes and afterwards you need to enter it again.

This PR checks if the user is in the docker group, add it if needed and remove the calls to sudo before the docker commands.

I know using the docker group is a bad practice (here) so if this isn't ok, I can refactor it to just not use sudo only if the user added themself to the group docker.

[warstrolo]

@hollowshiroyuki => I created a PR that check if current calling user is in docker group

[warstrolo]

Due to a comment, I added a prompt to add user to docker group

[Xephi]

Fixed by #7