Flatten marketing paths ahead of wiring up the websites

Drop the redundant documentation/marketing/ nesting inherited from the
plugin repos, so files sit at marketing/<plugin>/<page>.md. These paths
become raw URLs pasted into Elementor pages and ACF fields, so they are
much cheaper to change now than once sites reference them.

Fixes the four cross-plugin links for their new depth, and corrects the
README, which still pointed at the abandoned per-repo documentation/
folders instead of this repo.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

marketing/dotjuice-pagespeed/css-optimisation.md

@@ -0,0 +1,17 @@
+# CSS Optimisation
+
+Fewer, smaller, smarter stylesheet requests — one of the fastest ways to improve how quickly a page visibly appears.
+
+## The problem it solves
+
+A typical WordPress page loads CSS from half a dozen sources or more: your theme, Elementor, WooCommerce, and every plugin with its own styling. Each one is a separate request the browser must complete before it can safely paint the page — and by default, the browser won't show anything until every one of them has loaded. That's render-blocking, and it's a direct hit to your First Contentful Paint and Largest Contentful Paint scores.
+
+## How it helps
+
+Dotjuice Pagespeed combines your local stylesheets into a single optimised file and strips out everything that isn't needed to render the page — comments, unnecessary whitespace — without touching the actual styling. Fonts and CDN resources you don't control are left exactly as they are.
+
+For sites that want to go further, asynchronous CSS loading removes even that single combined stylesheet from the critical rendering path entirely: the browser paints the page using a small snippet of essential "critical" styling you provide, while the full stylesheet loads quietly in the background and takes over once ready.
+
+## The result
+
+Fewer HTTP requests, a smaller total payload, and — when paired with critical CSS — a page that visibly renders before its full stylesheet has even finished downloading.