Add XSLT stylesheets to folder RSS feeds

It'd be great to be able to attach an XSLT stylesheet to the generated RSS feed for any folder. Then I could style the feeds to match the rest of my site without having to do any server side dev.

XSLT is used to render XML (RSS/Atom in this case) in the browser. The [W3 spec for XSLT](https://www.w3.org/TR/2010/REC-xml-stylesheet-20101028/#dt-xml-stylesheet) has been around for about 15 years, and XSL stylesheets are widely used alongside RSS and Atom in blogs and podcasts. The XSLT document typically contains CSS styling and directives for transforming the XML (often into HTML).

Attaching a stylesheet is as easy as prefixing the RSS feed with, e.g.:

``

This could be accomplished by allowing additional query string and/or config params, such as `xsl_href` and `xsl_type`. There are a few other options, but only `href` is required to support linking in external sheets.

Thanks for considering, and for your efforts!