Add ignore word feauture and `!ignore <command> ` command

[OiYouYeahYou]

The feature would be a per channel ignore list filtering before and after translations. With the commands

• !ignore add <word> - Add a new word to channel ignore list
• !ignore remove <word> - Remove a word from channel ignore list
• !ignore list - List ignored words

These commands would also need moderator+ permissions