Make FetchMessage work for non-bot users

[PgBiel]

Basically just a shortcut to fetchMessages({ limit: 1, around: ID }), but it can be useful in case e.g. someone transfers their bot to an user account, or even be useful as a shortcut itself.

[rei2hu]

This is going to make fetchMessage return a collection for user accounts but not bot accounts, also it will return a random message for user accounts if the message doesn't exist while bot accounts get an unknown message error.

[devsnek]

this isn't consistant, you should map the return collection to the single message as expected

[devsnek]

if (!this.client.user.bot) return this.fetchMessages({ limit: 1, around: messageID }).then(c => c.first())