Improve accessibility for photosensitivity with user-controlled emote overrides for flashing emotes

[queerlorax]

Flashing animated emotes can be a health risk to people like me who are photosensitive. I would like to be able to set an override on my personal view for emotes that are problematic for me. This could be implemented different ways:

• Disable animation for a problematic emote so it stays locked on the first frame
• Change the problematic emote to grayscale (before choosing this consult with other photosensitive people to make sure that's effective for them too, but it would help me).
• Set problematic emotes to a slowed down animation timing to reduce flashing
• Block specific emotes (they would show up as plaintext)

Ideally the list of emotes affected would be stored in a user's account settings (not cookies) so it persists across devices.