feat(Sticker): updates, sticker packs, and guild stickers (#5867)

Co-authored-by: SpaceEEC <spaceeec@yahoo.com>
Co-authored-by: Antonio Román <kyradiscord@gmail.com>
Co-authored-by: Tiemen <ThaTiemsz@users.noreply.github.com>
Co-authored-by: Vlad Frangu <kingdgrizzle@gmail.com>
Co-authored-by: BannerBomb <BannerBomb55@gmail.com>
Co-authored-by: Noel <icrawltogo@gmail.com>
Co-authored-by: Sugden <28943913+NotSugden@users.noreply.github.com>

src/client/actions/GuildStickerUpdate.js

@@ -0,0 +1,20 @@
+'use strict';
+
+const Action = require('./Action');
+const { Events } = require('../../util/Constants');
+
+class GuildStickerUpdateAction extends Action {
+  handle(current, data) {
+    const old = current._update(data);
+    /**
+     * Emitted whenever a custom sticker is updated in a guild.
+     * @event Client#stickerUpdate
+     * @param {Sticker} oldSticker The old sticker
+     * @param {Sticker} newSticker The new sticker
+     */
+    this.client.emit(Events.GUILD_STICKER_UPDATE, old, current);
+    return { sticker: current };
+  }
+}
+
+module.exports = GuildStickerUpdateAction;