Invites: Invite types, invite flags & deprecate withExpiration opt

[conorwastakenwastaken]

Refs: Added type field to invites:

• https://github.com/discord/discord-api-docs/pull/6568
• https://github.com/discord/discord-api-docs/pull/7465

Added Guest Invite Flags:

• https://github.com/discord/discord-api-docs/pull/6247

Deprecates withExpiration option in any getInvite() functions - This is no longer used by Discord and the expiration date is now sent without supplying this query:

• https://github.com/discord/discord-api-docs/pull/7424
• https://github.com/discord/discord-api-docs/pull/7779

[conorwastakenwastaken]

To Do:

• [x] Guest invites flags
• [x] Invite types
• [ ] ~~with_permissions option when getting invites (https://github.com/discord/discord-api-docs/pull/7768 - tested myself)~~ apparently this isn't meant to be public or considered stable for bots
• [ ] Completely remove Invite#stageInstance???
• [ ] https://github.com/discord/discord-api-docs/pull/7849 ?? - tested myself

Is it worth completely removing Invite#stageInstance since that's been deprecated for a while? Will keep this PR as a draft until I get confirmation from abal or bsian about that