Cache JSON Responses of Emote Providers

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In the case that fetching the list of emotes through a provider fails, there should be a cached response to fall back to. This doesn't sound like a nightmare to implement, and would be imo a huge QoL change. It would feel great to still see emotes when a service is having a hiccup, especially since emote images/gifs are already getting cached.

To avoid any confusion, there should still be a system message when a cached response is used indicating that the request has failed.