feat(RichEmbed): add timestamp support for setTimestamp (#3061)

Author: SpaceEEC

src/structures/RichEmbed.js

@@ -140,10 +140,11 @@ class RichEmbed {
 
   /**
    * Sets the timestamp of this embed.
-   * @param {Date} [timestamp=new Date()] The timestamp
+   * @param {Date|number} [timestamp=Date.now()] The timestamp or date
    * @returns {RichEmbed} This embed
    */
-  setTimestamp(timestamp = new Date()) {
+  setTimestamp(timestamp = Date.now()) {
+    if (timestamp instanceof Date) timestamp = timestamp.getTime();
     this.timestamp = timestamp;
     return this;
   }

typings/index.d.ts

@@ -1030,7 +1030,7 @@ declare module 'discord.js' {
 		public setFooter(text: StringResolvable, icon?: string): this;
 		public setImage(url: string): this;
 		public setThumbnail(url: string): this;
-		public setTimestamp(timestamp?: Date): this;
+		public setTimestamp(timestamp?: Date | number): this;
 		public setTitle(title: StringResolvable): this;
 		public setURL(url: string): this;
 	}