feat: add possibility to select option via arguments

[jellekralt]

Hey! I needed a way to automate the script, which would only work through passing the option via arguments, so that's exactly what I added :)

[tr3kl0v]

Today there is the options to use flags. When using the -x flag for debugging reasons, this change generates the following error:

./stop-sauron.sh: line 58: [: -x: integer expression expected

[jellekralt]

Decided to rewrite it a bit and switch to using a flag (-o) for the option selection. I previously solved it without a flag because I figured it would be prepared for a possible subcommand setup later on. However, this needs bigger refactoring so for now lets keep it as a flag (which is much less complicated and guarantees interoperability with the -x flag).