Issue #3502062

1. Added base implementation of the filter 'UcwordsFilter' for the function 'ucwords'
2. Added unit test the filter 'UcwordsFilter'

Related to #3502062

src/Plugin/FapiValidationFilter/UcwordsFilter.php

+<?php
+
+namespace Drupal\fapi_validation\Plugin\FapiValidationFilter;
+
+use Drupal\Core\StringTranslation\TranslatableMarkup;
+use Drupal\fapi_validation\Attribute\FapiValidationFilter;
+use Drupal\fapi_validation\FapiValidationFiltersInterface;
+
+/**
+ * Fapi Validation Plugin for 'ucwords' filter.
+ */
+#[FapiValidationFilter(
+  id: 'ucwords',
+  label: new TranslatableMarkup('Ucwords'),
+  description: new TranslatableMarkup('Uppercase the first character of each word in a string.'),
+)]
+class UcwordsFilter implements FapiValidationFiltersInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function filter($value) {
+    return function_exists(' mb_convert_case') ?  mb_convert_case($value, MB_CASE_TITLE) : ucwords($value);
+  }
+
+}