Fix startup "welcome" sound sometimes not loading from skin for supporters
Adds SFX for rank changes to the in-game rank display - The DefaultRankDisplay component isn't visible by default, but can be added via the skin layout editor. The sound effects will only play if you add it to your skin layout, and if you're using a default skin.
If you're using a legacy/stable skin, you can skin the sounds using filenames rank-up and rank-down.
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