Sitemap generation fails for subfolder installs

[nilshoerrmann]

If a site is installed in a subfolder, e. g. example.com/my-site, the generation of the sitemap will fail because the XSLT path is hardcoded to /sitemap.xsl which resolves to example.com/sitemap.xsl instead of example.com/my-site/sitemap.xsl. See:

kirby-seo/classes/Sitemap/Sitemap.php

Line 69 in 1175d79

$doc->appendChild($doc->createProcessingInstruction('xml-stylesheet', 'type="text/xsl" href="/sitemap.xsl"'));

[tobimori]

Duplicate of #88