[Feature Request] Discord Rich Presence Support

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If it hasn't been discussed already, why not have Discord Rich Presence support? Once you add Livesplit as a game in Discord, you could show your friends and fellow runners the game and category you're running, and a live timer from Livesplit. This would be great for offline practice sessions while making sure that everyone can follow along with your run.
You could also show the number of attempts, your current split or even your current pace. And maybe you could even link to a SRL race or Twitch page in the future!

The issue names no files, tests, or entry points. Search the repository for the timer, game, category, split, and attempt concepts mentioned, then determine where a Discord integration could obtain them. Done should include a defined Rich Presence scope for the game, category, timer, and optional run details, with verification that the displayed information updates during a run.

Written by the indexing model from the issue text.