feat(Message): add support for crossposting

[CyberiumShadow]

Please describe the changes this PR makes and why it should be merged:

This PR adds supports for bots to crosspost messages in News Channels.

This resolves #4089 however is currently undocumented as per discord/discord-api-docs#1510

Status

• Code changes have been tested against the Discord API, or there are no code changes
• I know how to update typings and have done so, or typings don't need updating

Semantic versioning classification:

• This PR changes the library's interface (methods or parameters added)
  • This PR includes breaking changes (methods removed or renamed, parameters moved or removed)
• This PR only includes non-code changes, like changes to documentation, README, etc.

[jo3-l]

Slight typo in the example.

[bsian03]

Just before this gets merged, there's another endpoint to be added, see here

[HarmoGlace]

When will it be merged ?

[almostSouji]

when ever discord decides to document it (see the linked pull request on discord docs), as that signals "this is now completely implemented and (hopefully) won't change heavily going forward"

[CyberiumShadow]

Also when I decide to spend some time implementing the method to follow an announcements channel unless someone wants to PR that to my branch themselves

[iCrawl]

You could just fully read the message you liked from @almostSouji

[CyberiumShadow]

I know, I read it. In the PR for the developer docs there is the followers endpoint but I don't see it here. Will it be added ?

Eventually yes, I’m burnt out from discord development again so it might be a while until I personally add it to this PR.
Eitherway, there is still time regardless as Discord themselves are not officially supporting the endpoint yet.

Like I said earlier, you can wait for me to add it, or add it to my fork/branch via another PR which will show up here as well or add it yourself in a seperate PR

[advaith1]

docs pr merged 🎉

[TheNoob27]

since the post request returns the data of the message after being crossposted, shouldn't you update the message data? or will discord send a message update event after crossposting?

[vaporoxx]

There are no Message properties that change after crossposting, so I don't see why it should.

[wasdennnoch]

The message flags update to reflect that the message was crossposted; I believe that also fires a messageUpdate.

[TheNoob27]

Okay nvm i've checked, a messageUpdate event is fired