Increase fee limit to 30, add allow php 8 and 8.1

Author: Wawilow

.travis.yml

@@ -2,6 +2,8 @@ language: php
 
 php:
     - 7.4
+    - 8.0
+    - 8.1
 
 matrix:
     fast_finish: true

src/TRC20Contract.php

@@ -68,7 +68,7 @@ class TRC20Contract
      *
      * @var integer
      */
-    private int $feeLimit = 10;
+    private int $feeLimit = 30;
 
     /**
      * Base Tron object