add transaction id validator

src/Validators/TransactionIdValidator.php

@@ -0,0 +1,26 @@
+<?php
+
+/**
+ * @author Halil Beycan <halilbeycan0@gmail.com>
+ * @license MIT
+ */
+
+namespace Web3\Validators;
+
+class TransactionIdValidator
+{
+    /**
+     * validate
+     *
+     * @param string $value
+     * @return bool
+     */
+    public static function validate($value)
+    {
+        if (!is_string($value)) {
+            return false;
+        }
+        
+        return (preg_match('/^0x[a-fA-F0-9]{66}$/', $value) >= 1);
+    }
+}