module: add :lang flix

[CadeMichael]

Adding :lang flix module for doom emacs. I took most of the syntax hightlighting from https://github.com/jhckragh/flix-mode and added functions for executing flix commands and installing the flix.jar (the flix executable that is usually project specific and exists in each flix project). I also created a comint mode for interacting with the flix repl and some keybindings. I'm not sure if I laid everything out correctly but I tried to follow these resources. I think I probably butchered the git commit message but I can make changes if needed I'm just a bit confused as to what is needed. Please let me know what I should improve!

• https://github.com/doomemacs/doomemacs/blob/master/docs/contributing.org
• https://discourse.doomemacs.org/t/how-to-write-your-own-modules/86

---

• I searched the issue tracker and this hasn't been PRed before.
• My commits conform to the git conventions.
  • I believe so but I'm sure I made some mistakes this is my first commit to doom
• I am blindly checking these off.
• This a draft PR; I need more time to finish it.
  • I just have this checked because I haven't contributed before and want to confirm I didn't make a glaring mistake.

[CadeMichael]

[hpfr]

Instead of making a PR to Doom with a vendored major mode implementation, you might consider forking the archived package and developing from there. Doom modules, particularly for languages, try to limit themselves to setting sane defaults and integrating functionality of upstream packages for a good out-of-the-box experience.