feat(MessageEmbed): add #equals

[ImRodry]

Please describe the changes this PR makes and why it should be merged:
This PR adds the MessageEmbed#equals and the MessageEmbed#_fieldEquals methods (the latter being private) in order to allow for the comparison of two embed objects (while also accepting raw API embed objects). I stumbled across a scenario in one of my projects where I had to compare two embeds entirely so I figured I might as well add this to the library itself.

Status and versioning classification:

• 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
• This PR changes the library's interface (methods or parameters added)

[wutv]

serialize being v8.serialize

[ImRodry]

What is that supposed to mean @wutv

[wutv]

What is that supposed to mean @wutv

your code seems slightly unnecessary

[wutv]

that function basically has the same purpose as yours, except its smaller

[ImRodry]

Ok now try comparing two real embeds that are equal but attached to different objects. That's the point of this function and functions like this exist across the library so please show me better examples

[GodderE2D]

May I ask why _fieldEquals is private?

[ImRodry]

May I ask why _fieldEquals is private?

To be consistent with other methods such as ApplicationCommand#_optionEquals and because it doesn’t really make any difference since you can simply access it through MessageEmbed._fieldEquals, even in typescript I believe

Stale