Add a config toggle to disable the |> Run button

[jiribenes]

The |> Run button added in #28 should have a toggle in the configuration, which should be toggled by default (so that the |> Run is visible and usable by default), but can be turned off (so that the |> Run is completely hidden).

cc @b-studios

[b-studios]

This was more of a joke, I'm completely fine with having it always

[jiribenes]

I think it's fine to have a toggle like this anyways, esp. when the runner is very rudimentary: just running the whole file outside of a REPL...