per-channel emote blacklist (hide individual emotes) feature

[BennyyyBB]

Description

I recently saw a users message in the 7TV discord help channel asking for a feature that allows you to hide emotes in a specific twitch chat without having to deactivate the entire 7TV extension. A moderator answered that a feature like this doesn't really exist yet, there is only a way to fully hide an entire message, not only the emotes in it. Therefore I implemented a per-channel emote blacklist that hides specific emotes from chat without hiding the entire message.
Some channels add 7TV emotes to commonly used words, making chat unreadable, which was the point of the 7TV discord user asking for a way to hide them. Users should now be able to hide just the problematic emotes per channel.

• feature works for twitch, youtube and kick
• clicking a 7TV emote shows a "Hide in this channel" button in the emote card
• clicking a hidden emote's plain-text placeholder in chat re-opens the card with a "Show in this channel" option
• included an emote-blacklist option and list in the 7Tv chat settings under "Emotes"

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged