Adds a setting
@rickhanlonii Thanks a lot for a detailed PR!
I must admit that I'm a bit confused with the functionality you are trying to achieve. In #163 you mentioned "Slack user mentions". As far as I can see, pressing Tab in Slack is somewhat equivalent to pressing Down, not pressing Enter, i.e. it moves to the next suggestion rather than selecting the focused one. The URL bar in Chrome behaves the same. Am I missing something?