ci: Add test that themes appear in docs (#876)

* ci: Add test that themes appear in docs

* style: Formatted code with Prettier

---------

Co-authored-by: github-actions <41898282+github-actions[bot]@users.noreply.github.com>

Author: DenverCoder1

tests/OptionsTest.php

@@ -44,6 +44,22 @@ public function testThemes(): void
         }
     }
 
+    /**
+     * Test that all themes appear in the documentation (docs/themes.md)
+     */
+    public function testThemesInDocumentation(): void
+    {
+        $themes = include "src/themes.php";
+        $docContent = file_get_contents("docs/themes.md");
+        foreach (array_keys($themes) as $theme) {
+            $this->assertStringContainsString(
+                "`$theme`",
+                $docContent,
+                "The theme '$theme' is missing from the documentation (docs/themes.md).",
+            );
+        }
+    }
+
     /**
      * Test fallback to default theme
      */