chore: update kirby-seo plugin to v2.0.0-alpha.12

Update plugin from v1.1.2 to v2.0.0-alpha.12 for Kirby 5 compatibility.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

site/plugins/kirby-seo/classes/Sitemap/SitemapIndex.php

@@ -0,0 +1,101 @@
+<?php
+
+namespace tobimori\Seo\Sitemap;
+
+use DOMDocument;
+use Kirby\Cms\App;
+use Kirby\Cms\Page;
+use Kirby\Toolkit\Collection;
+
+class SitemapIndex extends Collection
+{
+	protected static $instance = null;
+
+	public static function instance(...$args): static
+	{
+		if (static::$instance === null) {
+			static::$instance = new static(...$args);
+		}
+
+		return static::$instance;
+	}
+
+	public function create(string $key = 'pages'): Sitemap
+	{
+		$sitemap = $this->make($key);
+		$this->append($sitemap);
+		return $sitemap;
+	}
+
+	public static function make(string $key = 'pages'): Sitemap
+	{
+		return new Sitemap($key);
+	}
+
+	public static function makeUrl(string $url): SitemapUrl
+	{
+		return new SitemapUrl($url);
+	}
+
+	public function toString(): string
+	{
+		$doc = new DOMDocument('1.0', 'UTF-8');
+		$doc->formatOutput = true;
+
+		$stylesheetUrl = kirby()->site()->canonicalFor("sitemap.xsl", true);
+		$doc->appendChild($doc->createProcessingInstruction('xml-stylesheet', 'type="text/xsl" href="' . $stylesheetUrl . '"'));
+
+		$root = $doc->createElementNS('http://www.sitemaps.org/schemas/sitemap/0.9', 'sitemapindex');
+		$root->setAttributeNS('http://www.w3.org/2000/xmlns/', 'xmlns:xhtml', 'http://www.w3.org/1999/xhtml');
+		$root->setAttribute('seo-version', App::plugin('tobimori/seo')->version());
+		$doc->appendChild($root);
+
+		foreach ($this as $sitemap) {
+			$root->appendChild($sitemap->toDOMNode($doc));
+		}
+
+		return $doc->saveXML();
+	}
+
+	public function isValidIndex(?string $key = null): bool
+	{
+		if ($key === null) {
+			return $this->count() > 1;
+		}
+
+		return !!$this->findBy('key', $key) && $this->count() > 1;
+	}
+
+	public function generate(): void
+	{
+		$generator = option('tobimori.seo.sitemap.generator');
+		if (is_callable($generator)) {
+			$generator($this);
+		}
+	}
+
+	public function render(Page $page): string|null
+	{
+		// There always has to be at least one index,
+		// otherwise the sitemap will fail to render
+		if ($this->count() === 0) {
+			$this->generate();
+		}
+
+		if ($this->count() === 0) {
+			$this->create();
+		}
+
+		if (($index = $page->content()->get('index'))->isEmpty()) {
+			// If there is only one index, we do not need to render the index page
+			return $this->count() > 1 ? $this->toString() : $this->first()->toString();
+		}
+
+		$sitemap = $this->findBy('key', $index->value());
+		if ($sitemap) {
+			return $sitemap->toString();
+		}
+
+		return null;
+	}
+}