fix(GuildManager): add missing types and converts

[NyanSpaghetti]

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

Updated PartialChannelData at /typings/index.d.ts#L4509 to match /src/managers/GuildManager.js#L83.
Added missing converts (userLimit, rateLimitPerUser, overwrite.type) to GuildManager#create.
Made PartialOverwriteData.type to take OverwriteType instead of string.

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

[Jiralite]

It seems it's a little more than the typings that aren't wholly correct with this.

1. A channel's rateLimitPerUser is not respected. You can easily see this in the code:

discord.js/src/managers/GuildManager.js

Lines 189 to 200 in 839974c

	for (const channel of channels) {
	if (channel.type) channel.type = ChannelTypes[channel.type.toUpperCase()];
	channel.parent_id = channel.parentId;
	delete channel.parentId;
	if (!channel.permissionOverwrites) continue;
	for (const overwrite of channel.permissionOverwrites) {
	if (overwrite.allow) overwrite.allow = Permissions.resolve(overwrite.allow).toString();
	if (overwrite.deny) overwrite.deny = Permissions.resolve(overwrite.deny).toString();
	}
	channel.permission_overwrites = channel.permissionOverwrites;
	delete channel.permissionOverwrites;
	}

There is no mention of converting a provided rateLimitPerUser to rate_limit_per_user here, so this doesn't actually work. This should work just like parentId and parent_id.

2. The overwrite type of a channel's permissionOverwrites documents to take a string, but discord.js does not resolve this string to an integer which is accepted by the API. This fails.

These were the only problems I found with GuildManager#create - I'd be grateful if you could include these also!

[blainegrissom]

I feel like the changes are good, but I don't know the code enough to feel comfortable saying "Yes this is good", so I will leave the judgement of approval to someone more knowledgeable in the code.

[Jiralite]

Mind modifying this to ChannelType|number?

discord.js/src/managers/GuildManager.js

Line 87 in 839974c

* @property {ChannelType} [type] The type of the channel