feat: Get corresponding Chat from Contact object and vice versa

close #269

index.d.ts

@@ -610,6 +610,11 @@ declare namespace WAWebJS {
 
     /** Returns the contact's profile picture URL, if privacy settings allow it */
     getProfilePicUrl: () => Promise<string>,
+
+    /** Returns the Chat that corresponds to this Contact.  
+     * Will return null when getting chat for currently logged in user.
+     */
+    getChat: () => Promise<Chat>,
   }
 
   export interface ContactId {
@@ -688,6 +693,8 @@ declare namespace WAWebJS {
     unarchive: () => Promise<void>,
     /** Unmutes this chat */
     unmute: () => Promise<void>,
+    /** Returns the Contact that corresponds to this Chat. */
+    getContact: () => Promise<Contact>,
   }
 
   export interface MessageSearchOptions {

src/structures/Chat.js

@@ -186,6 +186,14 @@ class Chat extends Base {
             return true;
         }, this.id._serialized);
     }
+
+    /**
+     * Returns the Contact that corresponds to this Chat.
+     * @returns {Promise<Contact>}
+     */
+    async getContact() {
+        return await this.client.getContactById(this.id._serialized);
+    }
 }
 
 module.exports = Chat;

src/structures/Contact.js

@@ -105,6 +105,17 @@ class Contact extends Base {
     async getProfilePicUrl() {
         return await this.client.getProfilePicUrl(this.id._serialized);
     }
+
+    /**
+     * Returns the Chat that corresponds to this Contact. 
+     * Will return null when getting chat for currently logged in user.
+     * @returns {Promise<Chat>}
+     */
+    async getChat() {
+        if(this.isMe) return null;
+
+        return await this.client.getChatById(this.id._serialized);
+    }
     
 }