Handle Ctrl-D in REPL and trigger toggling Quit Modal

[0xcefaedfe]

Implements #345

When Ctrl-D is received by handleREPLEvent, it checks if the prompt is empty (for both CmdPrompt and SearchPrompt cases). If it is empty, it calls toggleModal.

I'm new to Haskell in general, so if there's a better way to do this, please let me know.

[xsebek]

Thanks, @0xcefaedfe! I tested it and it works for me 👍

Please refactor the code with the text lens. Once you are done add the Merge me label.

[xsebek]

@0xcefaedfe you can apply the correct formatting by using fourmolu-0.4 (see #744) or use the helpful restyled bot output:

info     NOTE: you can manually apply these fixes by running:
info                                    
info         git checkout <your branch> 
info         curl https://restyled.io/gh/swarm-game/repos/swarm/jobs/2379705/patch | git am
info         git push                   

Because we keep the main branch formatted consistently, you should rarely see the formatter change any of the lines you did not edit in your PR. 😉

[byorgey]

@0xcefaedfe , congrats on having your first PR accepted to Swarm! We appreciate the contribution and we're really glad to welcome you as part of the community. In a minute we will send you an invite to the repo (see https://github.com/swarm-game/swarm/blob/main/CONTRIBUTING.md#i-have-push-access-to-the-swarm-repository-now-what ).