Added the field web_app_name to the class WriteAccessAllowed

Author: mircoianese

library/src/main/java/com/pengrad/telegrambot/model/WriteAccessAllowed.java

@@ -5,6 +5,12 @@
 public class WriteAccessAllowed implements Serializable {
     private final static long serialVersionUID = 0L;
 
+    private String web_app_name;
+
+    public String webAppName() {
+        return web_app_name;
+    }
+
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;