title: What characters are allowed as a shortcode tag and what sanitizing filter should I used for them?
body: <p>I working on a plugin where the user can define shortcode tags. What would you suggest to allow, my thought is only allow ascii characters.</p>
  
  <p>Also, how do you sanitize the input? I'm thinking maybe <code>stip_tags</code> and then regex to allow only <code>a-z, 0-9</code> or is there a better solution? Maybe wordpress filter would work? Or could I maybe use the filter wordpress uses for slugs? </p>