get csrf token in request; Test for prefix 'http-' in csrf token header

src/Pecee/Http/Request.php

@@ -147,6 +147,15 @@ class Request
         return $this->getHeader('php-auth-pw');
     }
 
+    /**
+     * Get the csrf token
+     * @return string|null
+     */
+    public function getCsrfToken(): ?string
+    {
+        return $this->getHeader('x-csrf-token') ?? $this->getHeader('http-x-csrf-token');
+    }
+
     /**
      * Get all headers
      * @return array