Fix RichInvite decoding
Fix RichInvite decoding

The RichInvite no longer contains the 'revoked' key. In addition,
decode the hash of the icon received for the relevant guild.

Instead of decoding a string channel type on the RichInvite and Invite,
decoding by an integer type.

SpaceManiac/discord-rs,jonalmeida/discord-rs,acdenisSK/discord-rs