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/html-optimisation.md

@@ -0,0 +1,15 @@
+# HTML Optimisation
+
+Trim the document itself, and stop paying for features WordPress loads by default that most sites never use.
+
+## The problem it solves
+
+WordPress ships with a handful of scripts and behaviours switched on for every site regardless of whether it needs them — emoji support for older browsers, embed discovery scripts, and more. Combined with unminified HTML output, that's requests and bytes spent on nothing your visitors actually benefit from.
+
+## How it helps
+
+Dotjuice Pagespeed minifies your final HTML output, strips WordPress's legacy emoji-detection script that modern browsers don't need, and gives you the option to disable oEmbed discovery entirely. On top of that, it automatically appends `font-display: swap` to your Google Fonts so visitors see readable text immediately in a fallback font rather than invisible text while the web font downloads — and it can add DNS prefetch hints for any third-party domain you rely on, shaving connection setup time off those requests.
+
+## The result
+
+A smaller HTML document, fewer unnecessary background requests, and text that's always visible to your visitors, never hidden waiting on a font file.