Added documentation for how to suppress next/prev/edit this page links

Details on how to do this changed recently so I thought it was about time to document these options here for the first time as I didn't add this when I first introduced them!

Author: Simon Prickett

README.md

@@ -103,6 +103,16 @@ authors: [suze,simon]
 
 * Note that multiple authors are supported as shown above.
 
+## Suppressing Next/Previous and Edit this Page Controls
+
+By default, each page has navigation at the bottom for the next and previous pages, as well as an "Edit this page" link.  If you want to suppress all or some of these, add the following extra front matter to your page's `.mdx` file:
+
+```yaml
+custom_edit_url: null
+pagination_next: null
+pagination_prev: null
+```
+
 ## How to modify the homepage banner
 
 In order to modify the homepage banner, you will need to edit the ```docusaurus.config.js``` file placed under the root of the repository.