Issue #3502056 - Add new plugin

Related to #3502056

src/Plugin/FapiValidationFilter/RtrimFilter.php

+<?php
+
+namespace Drupal\fapi_validation\Plugin\FapiValidationFilter;
+
+use Drupal\fapi_validation\FapiValidationFiltersInterface;
+
+/**
+ * Fapi Validation Plugin for Rtrim filter.
+ *
+ * @FapiValidationFilter(
+ *   id = "rtrim"
+ * )
+ */
+class RtrimFilter implements FapiValidationFiltersInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function filter($value) {
+    return rtrim($value);
+  }
+
+}