Added the parameter "protect_content" to AbstractSendRequest

Author: mircoianese

library/src/main/java/com/pengrad/telegrambot/request/AbstractSendRequest.java

@@ -29,4 +29,8 @@ public T allowSendingWithoutReply(boolean allowSendingWithoutReply) {
     public T replyMarkup(Keyboard replyMarkup) {
         return add("reply_markup", replyMarkup);
     }
+
+    public T protectContent(boolean protectContent) {
+        return add("protect_content", protectContent);
+    }
 }