Update README.md

Author: coofercat

README.md

@@ -1,2 +1,11 @@
-# pico-nestedpages
-Pico Plugin to let one page be embedded in another
+# Pico Nested Pages
+
+A [Pico CMS](http://picocms.org) plugin to allow one MD page embedded in another.
+
+This plugin adds a custom 'tag' to MarkDown that allows one page to be included in another. The page that's included is literally pasted into the page's MarkDown, and so gets rendered into HTML. The included file doesn't have to have the .md suffix, so it's possible to use files that Pico can't 'see'. With this, it's possible to have editable units used on one or many pages, for example to provide navigation, 'recent posts' or other such things (which may be hand-edited, or generated by some sort of offline process).
+
+To use the plugin, all that's required is the special tag with the path to a file to include. For example, if there's a file called /inc/navigation.md, then it can be included in a page with the following:
+
+ `@[/inc/navigation.md]`
+  
+The path to the included file must be relative to the content root (/content). The file you include is added verbatim before Pico rendering. If you accidentally decide to include a non-text file, you'll end up with unfortunately weird results.