Fix outdated sticker field name

[Andre601]

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Closes Issue: #1731

Description

Updated stickers to sticker_items in the EntityBuilder

[MinnDevelopment]

This needs to adjust the documentation on Message#getStickers to state that these stickers are partial, and limited to just the necessary information to render it. This means you only get the id, format type, and name.

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Unrelated to this pull request:

I noticed that, when sending a message, you still receive the stickers array in addition to sticker_items. Although, this is deprecated so we can probably just ignore it.

Another thing, the guild object might also contain rich sticker objects, which we could potentially add support for if discord would document it. There also is a GET/stickers/:sticker_id/guild endpoint that seems to be undocumented as well.

[Andre601]

This needs to adjust the documentation on Message#getStickers to state that these stickers are partial, and limited to just the necessary information to render it. This means you only get the id, format type, and name.

Adressed this.