Missing News and Store channel types

Created by: uwx

Summary

As per discordapp/discord-api-docs/issues/881, there are two new types of channels for verified servers: News and Store.

These are called GUILD_NEWS and GUILD_STORE in the docs, good luck figuring it out from there bucko

Thank you to @WamWooWamWooWamWooWamWooWamWooWamWooWamWooWam for pointing this issue out.