backport: Guild#{fetchEmbed,setEmbed} (#2778)

*  backport: Guild Embeds

* fix: Added missing return

* docs: Updated typings

src/structures/Guild.js

@@ -530,6 +530,26 @@ class Guild {
     return this.client.rest.methods.fetchVoiceRegions(this.id);
   }
 
+  /**
+   * The Guild Embed object
+   * @typedef {Object} GuildEmbedData
+   * @property {boolean} enabled Whether the embed is enabled
+   * @property {?ChannelResolvable} channel The embed channel
+   */
+
+  /**
+   * Fetches the guild embed.
+   * @returns {Promise<GuildEmbedData>}
+   * @example
+   * // Fetches the guild embed
+   * guild.fetchEmbed()
+   *   .then(embed => console.log(`The embed is ${embed.enabled ? 'enabled' : 'disabled'}`))
+   *   .catch(console.error);
+   */
+  fetchEmbed() {
+    return this.client.rest.methods.fetchEmbed(this.id);
+  }
+
   /**
    * Fetch audit logs for this guild.
    * @param {Object} [options={}] Options for fetching audit logs
@@ -1025,6 +1045,17 @@ class Guild {
     return this.client.rest.methods.updateChannelPositions(this.id, channelPositions);
   }
 
+  /**
+   * Edits the guild's embed.
+   * @param {GuildEmbedData} embed The embed for the guild
+   * @param {string} [reason] Reason for changing the guild's embed
+   * @returns {Promise<Guild>}
+   */
+  setEmbed(embed, reason) {
+    return this.client.rest.methods.updateEmbed(this.id, embed, reason)
+      .then(() => this);
+  }
+
   /**
    * Creates a new role in the guild with given information.
    * @param {RoleData} [data] The data to update the role with