Feature Request: Option to pause execution and open debug windows on `brk` instruction

[indigodarkwolf]

It may be useful for folks writing debuggable software if the brk instruction can pause execution and open debugging windows, similar to the behavior of stp. This should be guarded by an option setting, though, and default to false, to maintain backwards compatibility with x16emu. Toggling the setting should be exposed through UI and a command-line option.