Ask mods for permission before crossposting

[Toldry]

Before crossposting, send an automated message to the target subreddit mods for permission to post in their community.

The automated message will prompt the mods to do one of the following:

1. Approve the crosspost, and add u/AutoCrosspostBot as an approved user in the sub
2. Reject this specific crosspost
3. Reject this and all future crossposts, and ban u/AutoCrosspostBot from posting in the sub