Add onFocus hook to pane in layout

[alex35mil]

My primary use case would be ensuring I'm in locked mode when I focus the pane with my editor.

tab name="editor" focus=true {
  pane {
    borderless=true 
    onFocus={ SwitchToMode "Locked"; }
  }
}

[imsnif]

I really like this idea (only for consistency, better name it on_focus) - would you like to open an issue about it?

[alex35mil]

Snake case, of cource :) Creating an issue.