Add Attachment structure (#1731)

* Add Attachment structure

* Fix linter issues + @private

* Fixed array sends, also added embed sends

* fixed proving path to attachment

* fixed incorrect name assumption from path

* linting fix

* ;)

* im really good at this

* changes as requested by gus

and computer from #1459

* am a dum

* update webhook#send

* readonly addition to getters

* i... uh... oops

* farming deez commits

* fix webhook split

* removed some ugly

* removed .every checks

src/structures/Attachment.js

@@ -0,0 +1,73 @@
+/**
+ * Represents an attachment in a message
+ */
+class Attachment {
+  constructor(file, name) {
+    this.file = null;
+    this._attach(file, name);
+  }
+
+  /**
+    * The name of the file
+    * @type {?string}
+    * @readonly
+    */
+  get name() {
+    return this.file.name;
+  }
+
+  /**
+    * The file
+    * @type {?BufferResolvable|Stream}
+    * @readonly
+    */
+  get attachment() {
+    return this.file.attachment;
+  }
+
+  /**
+    * Set the file of this attachment.
+    * @param {BufferResolvable|Stream} file The file
+    * @param {string} name The name of the file
+    * @returns {Attachment} This attachment
+    */
+  setAttachment(file, name) {
+    this.file = { attachment: file, name };
+    return this;
+  }
+
+  /**
+    * Set the file of this attachment.
+    * @param {BufferResolvable|Stream} attachment The file
+    * @returns {Attachment} This attachment
+    */
+  setFile(attachment) {
+    this.file.attachment = attachment;
+    return this;
+  }
+
+  /**
+    * Set the name of this attachment.
+    * @param {string} name The name of the image
+    * @returns {Attachment} This attachment
+    */
+  setName(name) {
+    this.file.name = name;
+    return this;
+  }
+
+  /**
+    * Set the file of this attachment.
+    * @param {BufferResolvable|Stream} file The file
+    * @param {string} name The name of the file
+    * @private
+    */
+  _attach(file, name) {
+    if (file) {
+      if (typeof file === 'string') this.file = file;
+      else this.setAttachment(file, name);
+    }
+  }
+}
+
+module.exports = Attachment;