Allow moderators to access `!infr search` from `!user` embed through reactions.

[kosayoda]

Rationale

If the !user command targets a non-moderator in a moderation channel, make the infraction history directly accessible using a reaction. Currently, we almost always combine !user <user> with !infr search <user> and this change would make the infraction history directly accessible from the !user embed while taking up less vertical space.

[minalike]

I'd like this feature!