Improve Discord rich-presence

https://discord.com/developers/docs/rich-presence/best-practices

For reference, Splitgate 2's rich presence in Discord looks like the attached image (ugly, hidden information, no spaces).

The map thumbnail should be in the assets.large_image field, the map name should be in the assets.large_text field, details should include the gamemode, round fraction (i.e. Round 3/5), and score, state should say "In Match", "In Loadouts", "In Lobby", "In Postgame" (maybe), or "In Queue", timestamps.start should be set to the relevant start time (of the round or when you went back to lobby), timestamps.end should be set to when a relevant timer expires (such as gamemodes with timers or when the loadouts timer expires).

For ranked, an icon representing the rank should be the assets.small_image; for non-ranked, perhaps the selected faction could be there instead?