feat: allow for additional activation scripts

[ruben-arts]

Allow the activator to receive additional activation scripts from the user

[baszalmstra]

can just be Vec right?

[wolfv]

I am wondering if this is better vs. cloning the "activator" struct and adding the additional scripts along the way, like:

Activator<Bash> full_act = {
  activation_scripts: a.activation_scripts.chain(extra_activation_scripts),
  ...a
};

Then we don't need to add extra fields. We might also have to handle extra-deactivation scripts otherwise.