Specify that the additional partial member field is optional

[lipfangmoe]

I came across a parsing error in zigcord (https://codeberg.org/lipfang/zigcord) which had incorrectly assumed that the member field within mentions array of the Message Create gateway event was required.

Not quite sure if this falls under "subjective wording changes" in the contributing guidelines, but I feel that the statement is incorrect since it seems to assert that the member field is required.

The following message is an example of a message which contains a mentions property that contains users which don't have member fields. It is a message from the Wordle Discord Bot with a summary of those who have played wordle today, mentioning many guild members.

https://gist.github.com/lipfangmoe/6130b9a42a4396ddb4f62ec91c0a6527

[Rapptz]

For what it's worth, the member info is not present for users who got banned or kicked or just left so the assumption that it's required wouldn't have made sense to begin with.

[lipfangmoe]

@Rapptz I mean, when I was trying to statically type the entirety of the Discord REST API, I wasn't always thinking about the logic of why certain options are provided / not provided unless its relevant to the type. I was just writing down the types that the docs say :/ This definitely would've been helpful to have

[anthonydiscord]

Looks good, it broke the table though. Will you run npm run fix:tables and commit that?

[lipfangmoe]

Sure thing - meant to do that when I first saw the CI error, but entirely forgot about it! Thank you for reminding me this PR existed ahaha