feat: custom user Agent in Client (#271)

* Added Option to Custom User Agent in Client

* Update Typescript Index

* Delete Variable UserAgent From Client

* Update Variable UserAgent to userAgent

index.d.ts

@@ -215,6 +215,8 @@ declare namespace WAWebJS {
     takeoverOnConflict?: boolean,
     /** @default 0 */
     takeoverTimeoutMs?: number,
+    /** @default 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.109 Safari/537.36' */
+    userAgent?: string
   }
 
   /** Represents a Whatsapp client session */